TEACHERS COLLEGE, COLUMBIA UNIVERSITY TEACHER SELECTION AND EFFECTIVENESS IN TURKEY M. ALPER DINCER 6/8/2011 [In Turkey, a teacher hiring system based on subjective evaluation was replaced with a teacher selection model which operates through centralized testing. This study evaluates the impact of this new teacher selection policy on mathematics and science test scores of 8th graders. The findings show that a 0.17 standard deviation increase in test scores can be attributed to the policy change and the estimated impact is much higher for below median achievers and students with female teachers. The findings also suggest that the new policy assigns more teachers to relatively poor schools and classrooms.] 1. Introduction: test scores The primary and secondary education systems in Turkey have been undergoing a restructuring since late 1990s in response to swift developments in the formation of its economy and demographics of its young population. One of the main goals of this restructuring is to increase the quality of education in Turkey (Aksit, 2007). Thus it is important to investigate empirically whether these reform efforts achieve the intended outcomes or not. Trends in International Mathematics and Science Study (TIMSS) and Program for International Student Assessment (PISA) periodically measure student achievement on an international scale and assemble information about students, families and schools. With the help of these projects it is possible to track student achievement in participating countries and make cross-country comparisons. A representative set of the student body in 8th grade which is the final grade of mandatory schooling in Turkey participated in TIMSS 1999 and 2007. The average mathematics and science scores of students in Turkey in 1999 were 429 and 433 whereas the international average scores were 487 and 488, respectively. Similarly the average mathematics and science scores of students in Turkey in 2007 were 433 and 454 whereas the international average scores were 488 and 500, respectively: The students in Turkey performed lower than the average international student achievement. On the other hand Table 1 gives the percentages of students in Turkey reaching the TIMSS international benchmarks and these figures present the another pattern in mathematics and science: There are more students in advanced and high international benchmark levels and there are fewer students in low international benchmark levels in 2007 relative to 19991. As a cautionary note, it should be stated that these percentages are not directly comparable for Turkey between 1999 and 2007 (Martin, et al., 2008a, 2008b). Table 1: The percentages of students reaching the TIMSS international benchmarks Advanced High Intermediate Low 1999 1 6 20 38 2007 5 10 18 26 1999 1 5 19 37 Science 2007 3 13 24 31 Source: (Martin et al., 2001a), (Martin et al., 2001b), (Martin, et al., 2008a), (Martin, et al., 2008b) Mathematics In order to render the TIMSS data more comparable I kept the countries for which data is available in TIMSS 1999 and 20072 and standardized mathematics and science test scores for this set of countries with mean 0 and standard deviation 1. This analysis suggest that average mathematics achievement in Turkey increased by 0.17 standard deviation and average science achievement increased by 0.21 standard deviation from 1999 to 2007. Figure 1 presents kernel density estimations of standardized mathematics and science scores in Turkey and all of the countries. These estimations suggest two important points: First, compared to 2007, the density of students who perform below cross-country average were much higher in 1999. Second, the density of students who perform above cross-country average were much lower in 1999. 1 For the description of these benchmark proficiency levels please see (Martin, Mullis, Foy, & Olson, 2008b) and (Martin, Mullis, Foy, & Olson, 2008a). 2 Bulgaria, Taiwan, Cyprus, Czech Republic, Hong Kong, Hungary, Iran, Israel, Italy, Japan, Jordan, Korea, Malaysia, Romania, Russia, Singapore, Slovenia, Thailand, Tunisia, Turkey and United States. The sample size is 195242 and represents a student population of 25 millions. Figure 1: Kernel density estimations of TIMSS 1999 and 2007 for Turkey and a selected set of countries PISA offers more definitive information about the trend of learning outcomes of students in Turkey. Similar to TIMSS, PISA measures the reading, mathematics and science test scores of a student body which is representative for the 15-year old student population in each participating country. Turkey participated PISA in 2003, 2006 and 2009 and the trend in mathematics score is comparable between 2003 and 2009 and the trend in science test score is comparable between 2006 and 2009 (OECD, 2010). According to PISA results average mathematics score of 15-year old students in Turkey increased by 22 points (more than 0.2 standard deviation) and average science score of 15-year old students in Turkey increased by 30 points (approximately 0.3 standard deviation) (OECD, 2010). PISA data also shows that in which segment of the student body these improvements occurred. The percentage of students that falls below the proficiency level 2 decreased from 52 to 42 percentages in mathematics and from 47 to 30 in science. On the other hand the percentages of top performers did not show any increase or decrease between the respective periods (Figure 2). Trend of the average student achievement in mathematics and science in Turkey highlight at least three important facts. First, for a period which follows 1999, average student achievement in mathematics and science is increasing for the student population which is either in grade 8 or 15 years old. Second, this increase in average student achievement is not homogenous. Indeed it is more intensive on the lower part of the student achievement distribution in these subjects. Third, these improvements are not due to inflation in test score scales; average performance of students in Turkey is converging to Source: (OECD, 2010) -20 + o o o o o o o o o o o o o o o o o o o o o o + o o o o o o o o o o o o + o o - 20 15 10 5 0 -5 -10 Percentage of students below proficiency Level 2 27 -25 35 30 25 o 2009 Indonesia o Tunisia - Brazil - Thailand o Mexico - Uruguay o Turkey - Serbia o Greece - Russian Federation o Italy - Luxembourg + Spain o Portugal - United States o Latvia o France + Czech Republic + Hungary o Sweden + Slovak Republic o Ireland + 2009 Poland o Belgium + Germany o Norway o Denmark o Iceland + Australia o -15 Switzerland o -10 New Zealand -5 Japan o 0 Netherlands o 5 Canada o 10 Macao-China o 15 Liechtenstein o 20 Korea o 25 Hong Kong-China o 30 Percentage of students below proficiency Level 2 35 Finland o Czech Republic 0 Ireland 0 Sweden 0 France 0 Belgium 0 Netherlands 5 Denmark 1 Australia 1 Iceland 0 Canada 7 Japan 36 New Zealand Luxembourg 10 Finland 28 Macao-China 58 Spain 67 Slovak Republic 76 Latvia 78 Russian Federation 92 OECD average-28 98 Hungary 97 Liechtenstein 97 Thailand 74 Norway 48 Korea 47 Hong Kong-China 46 United States 37 Uruguay 33 Poland 29 Serbia 29 Switzerland 15 Germany 4 Indonesia 5 Tunisia 0 Italy 0 Portugal 0 Greece 0 Turkey 1 Brazil 0 Mexico 0 Score point change in mathematics performance between 2003 and 2009 40 Finland Korea Hong Kong-China Estonia Canada Macao-China Japan Chinese Taipei Liechtenstein Australia Poland Netherlands New Zealand Switzerland Hungary Latvia Slovenia Germany United Kingdom Ireland Norway Portugal Denmark Lithuania Czech Republic Iceland Belgium United States Spain Croatia Sweden Slovak Republic France Italy Russian Federation Luxembourg Greece Turkey Chile Israel Serbia Bulgaria Romania Uruguay Thailand Jordan Mexico Argentina Montenegro Tunisia Colombia Brazil Qatar Indonesia Azerbaijan Kyrgyzstan Qatar 0 Turkey 0 Portugal 0 Korea 0 Tunisia 0 Brazil 0 Colombia 1 Italy 0 Norway 1 United States 3 Poland 2 Romania 10 Argentina 23 Chile 11 Japan 14 Kyrgyzstan 12 Serbia 12 Hong Kong-China 13 Mexico 13 Bulgaria 56 Switzerland 31 Iceland 15 Germany 38 Latvia 38 Thailand 34 Lithuania 47 Denmark 47 France 59 OECD average -33 24 Slovak Republic 70 New Zealand 72 Israel 86 Australia 93 Macao-China 94 Spain 97 Ireland 95 Uruguay 84 United Kingdom 80 Russian Federation 83 Hungary 79 Liechtenstein 70 Luxembourg 43 Netherlands 69 Greece 57 Estonia 43 Belgium 39 Canada 11 Jordan 21 Croatia 13 Slovenia 2 Sweden 6 Azerbaijan 6 Finland 2 Montenegro 0 Indonesia 14 Chinese Taipei 2 Czech Republic 2 Score point change in science performance between 2006 and 2009 Figure 2: PISA indicators 90 2003 80 70 60 50 40 30 20 -20 10 0 100 2006 90 80 70 60 50 40 30 20 -15 10 0 international benchmarks as they are defined either by TIMSS or PISA. This convergence is pretty quick at least according to the measure PISA provided. These facts immediately raise several questions: Are these changes in student achievement related to restructuring in the education system in Turkey? If yes, which aspects of the reform initiative in Turkey did lead to higher learning outcomes in mathematics and science? Is it possible to identify the channels through which the policy intervention leads to increases in student achievement? This study attempts to offer some candidate answers to these questions. 2. Possible explanations OECD (2010) stresses the role of the Basic Education Programme (BEP) in increasing learning outcomes in Turkey. This World Bank supported programme defined the framework of reform initiative in education according to the Law No. 43063. With this legislation in August 1997, Ministry of National Education (MONE) aimed to achieve increasing primary school education, improving the quality of education and overall student outcomes, closing the performance gap between boys and girls, providing equal opportunities, matching the performance indicators of the European Union, developing school libraries, increasing the efficiency of the education system, ensuring that qualified personnel were employed, integrating information and communication technologies into the education system and creating local learning centers, based in schools, that are open to everyone4. In response to these efforts the attendance rate in the eight-year primary education system soared from 85 to 100 percent. Similarly, the attendance rate in pre-primary education 3 4 http://mevzuat.meb.gov.tr/html/24.html http://www.meb.gov.tr/Stats/Apk2002/502.htm system increased from 10 to 25 percent. These increases led to an expansion of the education system by 3.5 million pupils. These quantitative expansions were accompanied by qualitative improvements: During the same period average class size was reduced from approximately 40 to 30; conditions were improved in all rural schools and computer laboratories were established in every primary school. Lastly the cost of the BEP exceed the equivalent of USD 11 billion (OECD, 2010). OECD (2010) as well as MONE also highlight the importance of recent curriculum change in mathematics and science (TTKB, 2008): New curriculum were launched in the 2006-2007 school year, starting from the 6th grade. Similarly, mathematics and language curriculum were also updated and starting from the 9th grade in the 2008-2009 school year a new curricula of science was in force. According to the Board of Education (TTKB) the aim of this change was to update the content of school education as well as to change the teaching philosophy and culture within schools. Although the new curriculum are the preferred explanation of MONE and some other research institutions in Turkey5 for the increased learning outcomes, the connection is not clear and there is a problem with this specific explanation: First, given that TIMSS covers the period between 1999 and 2007 the new curriculum cannot not explain the improvement in learning outcomes which is evident in TIMSS data. Second, average achievement in mathematics in PISA is not comparable between 2006 and 2009. Thus the timing of the inception of the new curriculum and the increase in average mathematics achievement do not overlap. Third, the students who were subject to the curricula change in science are 9th graders which constitute only a portion of the PISA 2009 sample; moreover they experienced the new curricula only for two semesters. It is not clear 5 http://bit.ly/iVZojN; http://bit.ly/j5tOLv whether these students may drive a 0.3 standard deviation increase in science between 2006 and 2009. As mentioned earlier, one of the targets of the BEP was to ensure that qualified personnel were employed. In line with this goal teacher selection policy was changed in 2002 which might have affected teacher quality in public primary and secondary institutions. In the following I will present a brief review on teacher quality and then go on with the nature of the teacher labor market and testing system in Turkey. 3. Why teacher quality is important? Learning outcomes are affected by many factors, including: students’ ability, potential, enthusiasm and behavior; school management, resources and atmosphere; curriculum and content; and teacher ability, preparation, attitudes and practices. Schools and classrooms are elaborate and dynamic mediums and identifying the education production function and underlying technology continues to be a major challenge of educational research. This problem has many aspects ranging from research design and methodology to data availability. Usually researchers are forced to use measures which are only partial indicators of learning and in many cases it is not possible to apply the relevant methodologies. Therefore the results, interpretations and policy implications of such studies are regularly questioned. Keeping this caveat in mind some general inferences can be drawn from the body of research on the determinants of learning. First, out-of-school factors such as the ability, motivation, parental characteristics, neighborhood and socioeconomic status are the strongest predictors of learning and it is not easy to change these factors through policy intervention in the short run. Second, among the factors which are open to policy influence teacher quality is the most important school input affecting learning. Santiago (2002), Schacter and Thum (2004) and Eide, Goldhaber and Brewer (2004) present extensive and detailed reviews of this line of research. The difference in teacher quality may lead to substantial differences in student achievement. Empirical investigations analyzing the impact of total teacher effect on learning usually estimate individual teacher effects by making use of student-teacher matched panel data sets with teacher fixed effects and then construct a teacher effectiveness distribution based on individual teacher effects. The studies employing this methodology suggest that teachers differ substantially in terms of effectiveness. Most recent studies show that one standard deviation increase in teacher quality is associated with 0.1-0.15 standard deviation increase in mathematics test scores of primary and secondary school students (Hanushek & Rivkin, 2010). In order to understand the relative significance of teacher quality Rivkin et al. (2005) analyze a unique matched panel data from the UTD Texas Schools Project which allows them to identify teacher quality based on student performance. They conclude that the contribution of a ten student reduction in class size is less than that of a standard deviation increase in teacher quality. In another study, Rockoff (2004) analyzes a 10-year panel data of test scores and teacher assignments to understand how much teachers affect learning. The panel structure allows him to focus on differences in the performance of the same student with different teachers and to decompose the variation in teacher quality from variation in students’ characteristics. His analysis shows that variation in teacher quality explains 23 percent of the variation in the test scores which is potentially open to policy influence. In addition to these findings, researchers in this literature also tried to decompose total teacher effect into subcomponents of measured teacher characteristics such as teacher experience, teacher education, teacher certification etc. However these studies are in consensus that measured teacher characteristics are not much associated with estimated individual teacher effects (Aaronson, Barrow, & Sander, 2007; Hanushek, 1992; Rivkin, et al., 2005; Rockoff, 2004). This finding is in line with the meta-analyses conducted on school resources and teacher characteristics: Hanushek covered a significant number of studies from US in three reviews. He compiled 147 separately estimated educational production functions from 33 publications (Hanushek, 1986). Later he updated this survey twice. In his 1989 study he compiled 187 estimations from 38 articles (Hanushek, 1989) and in 1997 he covered a set of publications available through 1994. This set included 90 publications and 377 separate estimates (Hanushek, 1997). The selection criteria to be included in these surveys were to be published in a book or refereed journal, relating some objective measure of student output to family and school characteristics, providing information about statistical significance of estimated relationships (Table 2). Hanushek draws three main conclusions from these summaries: First, the estimates of educational production functions are not promising for teacher education. These studies fail to establish a strong and consistent relationship between teacher education and higher student achievement. Second, the majority of the estimated coefficients for teacher experience point in the correct direction and 30 percent of the estimated coefficients exceed the conventional statistical significance level of 5 percent. However the results for teacher experience are hardly overwhelming; the relationship between teacher experience and student achievement is strong only relative to other school inputs6. Hanushek (1986, 1989, 1997) claims that the positive association between teacher experience and student achievement may be due to possible selection effects. He stresses that this finding may be a result of experienced teachers being allowed to select schools and classroom with higher achieving students. Third, among all of the teacher characteristics (as well as other explicit measures) higher teacher test scores are most consistently associated with stronger learning outcomes. Table 2: Percentage Distribution of Estimated Effect of Teacher Characteristics on Student Performance 1986 1989 1997 Statistically Statistically Statistically significant & Positive significant & Positive significant & Positive positive positive positive Teacher education 6 30 7 35 9 Teacher experience 30 60 29 60 29 Teacher test score 28 78 26 58 37 Source: Author’s calculations from the studies of Hanushek (1986, 1989, 1997) 42 59 64 These meta-analyses cover only studies from US and the evidence from other developed countries are scarce. To my knowledge there is not any meta-analysis for developed countries other than US. However the study of Hanushek and Luque (2003) gives insight at this front. They analyze TIMSS data for 18 developed and developing countries7 and suggest that the findings are very similar to the meta-analyses which only include studies from US. 6 Hanushek also summarizes estimated coefficients for student teacher ratio, per pupil spending, facilities and administrative inputs. 7 Canada, Cyprus, Czech Republic, Greece, Hong Kong, Ireland, Japan, Latvia, Netherlands, New Zealand, Norway, Portugal, Thailand, Scotland, United States and Slovenia As for developing countries, the first comprehensive meta-analysis dates back to 19878. Fuller (1987) reviews 60 studies investigating student achievement in developing countries. Later Fuller and Clarke (1994) expand Fuller’s 1987 study by surveying an additional 47 studies published between 1987 and 1993. These meta-analyses included studies that used at least some measure of student’s social class as a control variable. A year later Hanushek (1995) conducted a larger survey with the same criteria for study selection based on his previous study (Harbison & Hanushek, 1992). Lastly, very recently, Glewwe et al. (2011) conducted a meta-analysis on developing countries and extracted estimates from studies published between 1990 and 2010. They filtered a very large pool of studies according to their methodological approaches and ended up with 79 studies which use at least simple OLS with at least one family background, school expenditure, teacher and one additional school variable as controls. 43 of these 79 studies had a more complicated identification strategy such as randomized controlled trials, difference-in-differences, regression discontinuity and matching designs. These meta-analyses which cover the last three decades consistently show that teacher test score is a stronger indicator of teacher effectiveness when compared with teacher education and teacher experience and this distinction appears to be more pronounced in developing countries than developed countries. Therefore, especially in developing countries, teacher test scores may provide valuable input for policy makers in designing teacher selection and hiring mechanism (Table 3). Interestingly, there are some studies from Turkey which point to the same direction: Several studies which analyze PISA 2006 data for Turkey suggest that students who were 8 Relatively smaller surveys appeared earlier (Heyneman & Loxley, 1983; Schiefelbein & Simmons, 1981; Simmons & Alexander, 1978). taught by teachers who passed rigorous testing procedures are associated with higher test scores (Alacaci & Erbas, 2010; Dincer & Uysal, 2010). Table 3: Percentage Distribution of Estimated Effect of Teacher Characteristics on Student Performance in Developing Countries Glewwe et al. (2011) Fuller Fuller and Clarke Hanushek (1987) (1994) (1995) inc. OLS exl. OLS Teacher education 46 54 56 33 15 Teacher experience 43 40 35 27 18 Teacher test score 100 100 55 65 Source: Authors calculations from the studies of Fuller (1987), Fuller and Clarke (1994), Hanushek (1995) and Glewwe et al. (2011) 4. Basic characteristics of teacher labor market in Turkey The main characteristic of teacher labor market in Turkey is excess supply of teachers. As of 2010, approximately 327 thousand teachers are in line to be employed by public sector and the number of applicants is three to four times higher than the number of the opening teaching positions (Figure 3). This army of inactive teachers represents a significant population given that the number of employed teachers in the public sector is 680 thousand. Whereas MONE predicts that the desired level of employed teachers in public education system is 717 thousand9 the gap between supply and demand of teachers widens cumulatively. As of 2010, MONE demanded 782 mathematics teachers and it received 2798 applications. For science these figures are 861 and 354610, respectively and the gap more or less is evident in every subject; thus excess supply is not specific to some of the subjects. 9 http://icden.meb.gov.tr/digeryaziler/MEB_ic_denetim_faaliyet_raporu_2009.pdf http://personel.meb.gov.tr/ana_sayfa.asp 10 Figure 3: The number of open positions and applicants by subject 4000 3500 3000 2500 2000 1500 1000 500 0 Math Science Physics Biology Chemistry and Tech # Open positions # Applicants Source: Author’s own calculations from http://personel.meb.gov.tr/ana_sayfa.asp A reasonable explanation of this situation may be the presence of very attractive teacher salaries. However teacher salaries in Turkey are not attractive at all. In the public sector the starting annual salary of a teacher is around 14000$ and it does not improve much with experience (Figure 4). The salary of a teacher with 15 years of experience is around 16000$ (OECD, 2009). Dolton and Gutierrez (2011) present a cross-country analysis of teacher pay and performance by taking the relative earning distribution in each country into account. Their analysis confirms that the teacher salaries are not especially attractive in Turkey and the salary-experience profile is flat (Figure 5). Therefore starting salaries and expectation of higher salaries in the teaching profession cannot explain the excess supply in the teacher labor in Turkey. Another important feature of teacher labor market is that all public servants in Turkey are protected by law and unions and job separation is a very unlikely event. Therefore teaching profession offers substantial job security and given the presence of very high chronic unemployment rates, individuals value job security heavily. Figure 4: Ratio of salary after 15 years of experience to GDP per capita 2.5 2 1.5 1 0.5 Korea Germany Portugal Japan Scotland New Zealand Switzerland Mexico Spain England Czech Republic Turkey Slovenia Ireland Belgium (Fl.) Australia OECD average Greece Netherlands Belgium (Fr.) Denmark Chile Finland Austria Italy France United States Sweden Luxembourg Hungary Iceland Norway Israel Estonia 0 Source: (OECD, 2009) Figure 5: Average teacher wage-experience profile in Turkey Source: (Dolton & Marcenaro Gutierrez, 2011) One study (Caner & Okten, 2010) analyzes the college major choice decision in a risk and return framework using university entrance exam data from Turkey and shows that individuals are very sensitive to risk during career choice. It should be also noted total enrollment in education faculties in Turkey also increased steadily in time: The annual enrollment increased from 33 thousand in 2007 to 45 thousand in 2008 and 54 thousand in 2009 and MONE expands the teaching force by approximately 40 thousand each year11. Thus a combination of an intense demand for job security and increased quotas of education faculties may provide a more sensible explanation for the excess supply in teacher labor market in Turkey. 5. Legal framework of teacher selection in Turkey There are three main legal sources which regulates hiring of teachers in Turkey. First, teachers working in the public sector are subject to Law No. 657. This law defines the rights as well as legal obligations of public servants since 1965. Second, the regulation of the tests concerning the assignments of public servant candidates describes the testing procedure for public servant posts since 2002. Third, MONE’s regulation of teacher assignment and replacement explains how the testing procedure and test results apply to teacher selection process. The current version of this regulation is legislated in 2010 and it has changed many times in the past according to the needs of MONE. The regulation of the tests concerning the assignments of public servant candidates basically forms a turning point in teacher selection; because it causes a radical change in teacher selection policy in Turkey. 11 http://www.ogretmenportali.net/HaberGoster/228716e4-64bf-4b55-bb17-fc0ee89baf38/atanmayan-ogretmenordusu-buyuyor.aspx Under the teacher regime system before the legislation of this regulation, i.e. prior 2002, any eligible teacher candidate was able to apply to any available position announced by MONE. The applications were processed in provincial offices of MONE and then the final decision was announced by the headquarters of MONE in the capital, Ankara (Figure 6). Figure 6: A presentation of teacher selection system before 2002 This system was a cause of concern of MONE as well as State Planning Organization (SPO) (SPO, 1989). One of the main issues of the pre-2002 system was a constant imbalance of teacher population across regions. According to the Research and Development department of MONE, one preliminary report of the 1993 National Education Assembly stressed that more than 10 percent of teachers employed by MONE in urban areas did not teach a single class. Another issue documented in MONE’s records was that political pressures and interventions damaged the fairness and equality principles in teacher employment and caused unrest among teachers (EARGED, 1995). Indeed this was well-known publicly that to have connections in provincial offices as well as in the capital was essential to get hired. Thus nepotism was a general worry concerning this selection process. Following the legislation of the above mentioned testing regulation Center of Measurement, Selection and Placement (OSYM) launched a central examination process which is known as Public Servant Selection Examination (KPSS). This exam has two sessions: For the first session teacher candidates have to answer 120 multiple choice questions about Turkish, Mathematics, History, Citizenship, General Culture and Geography in 180 minutes. In the second session teacher candidates have to answer 120 multiple choice questions about educational psychology, educational programs and teaching and educational guidance in 180 minutes. Then applicants are assigned to teaching positions centrally by MONE according to their test scores in the central examination and their ranked list of preferred teaching positions (Figure 7). OSYM conducts the exam annually and if a teacher candidate fails to be placed to a teaching position then s/he has to take the exam again in the following year. Figure 7: A hypothetical presentation of teacher selection after 2002 Under this teacher selection regime it is not possible to game the hiring process and it is also not possible to leverage nepotism in order to get a teaching position. Thus it is reasonable to claim that the central examination and allocation of teaching positions based on test scores address the problem of lack of fairness. However two questions remain to be answered: Does the new system ensure that the qualified teachers are employed? Does this system have an impact on the regional imbalance of teacher population? The first question is critical because it was one of the main goals of BEP. The second question is critical because the imbalance constitutes a chronic problem of education system (EARGED, 1995; SPO, 1989). 6. Data In order to answer these research questions I employ TIMSS 199912 and TIMSS 200713 data sets. These data sets have some important qualities which render them very suitable to investigate these issues. First, as mentioned earlier, these projects assess a representative set of 8th graders. 8th grade is the final grade of primary education in Turkey and hence students in the sample should have spent at least a couple of years in their current institutions. Second, it is possible to link teachers to students in the same classroom which makes these data sets especially attractive for this analysis. Third, TIMSS project conducts four questionnaires, i.e. student, school, mathematics and science teacher questionnaires. The student and teacher questionnaires contain extensive information about demographic and socioeconomic characteristics of students and teachers. In addition, the school questionnaire contains information on school location, resources and governance. Fourth, the information collected in 1999 and 2007 is comparable to a certain extent. The questionnaires in 1999 and 2007 do not overlap extensively; however most of the essential information is available in both data sets. Fifth and most importantly, the policy change which is subject to the evaluation in this study falls into the middle of 1999 and 2007, the dates Turkey participated to TIMSS. 12 13 http://timss.bc.edu/timss1999.html http://timss.bc.edu/timss2007/index.html This allows me to have a reasonable number of observations who are subject to the policy change which was launched in 2002. Lastly, the teacher experience is reported in years such as 1, 2, 3 etc. but not in year categories such as 0-4, 5-8 etc. This distinction is crucial for this analysis because the data on teacher experience in TIMSS allows me to define the treatment and control groups with respect to the inception date of the new policy. 7. Methodology and empirical analysis For the empirical analysis, first, I merged the student, school and teachers data sets for 1999 and 2007 and compiled the 1999 and 2007 TIMSS data sets. Then I defined the treatment group as the students whose teachers have four or less years of experience. This assumption is necessary because I do not observe whether the teachers were selected via central examination or not. Thus I assume that this definition of treatment group approximates the ideal case. The justification of this assumption is based on the timing of the TIMSS application and the central examination. The first central examination in Turkey was conducted in July 2002; OSYM announced the test scores in August 200214 and MONE distributed the teaching posts based on announced test scores in September, October and November 200215. On the other hand TIMSS 2007 application in Turkey was conducted in April, May and June 2007 (Olson, Martin, Mullis, & Arora, 2008). Thus a teacher who was selected with the first central examination should have assigned to a post as early as September 2002 and the same teacher should have answered TIMSS teacher questionnaire as late as June 2007. According to this hypothetical example this teacher 14 15 http://www.osym.gov.tr/belge/1-6128/2002-sinavlari.html http://personel.meb.gov.tr/sayfa_goster.asp?ID=207 could not have five years of experience at the time of TIMSS application. Therefore the treatment group is assumed to be as defined above. However this is an imperfect measure of selection via central examination: First, teacher turnover leads to measurement error; because it is possible to quit and return teaching which may be an issue especially for female teachers who may substitute teaching with child raising for a couple of years. Second, OSYM conducted another central examination which is known as Central Elimination Examination for Institutions (KMS) in 200116. KMS was different than KPSS and it is not clear how many teaching posts were distributed based on KMS scores as well as whether KMS scores were the sole determinant of the teacher assignments. This issue may also lead to measurement error. Keeping these shortcomings in mind I basically compare the difference of average student achievement between treatment and control groups in 1999 and 2007 with a basic differences-in-differences approach. The main assumption of this approach is that the change in mean test scores that the control group experiences over time reflects the same change that the treatment group would have experienced had they not been exposed to the treatment. Another important assumption of differences-in-differences approach is that unobserved characteristics have the same distribution across time points and across treatment groups. I will discuss the validity of these assumptions in the subsequent sections. For the differences-in-differences analysis I estimated the following regression models: 16 http://www.osym.gov.tr/belge/1-12485/2001-sinavlari.html Table 4: Difference-in-Differences estimations In these regression models ๐ฆ๐๐๐ ๐ represents the dependent variable which is either the mathematics or science test score. However it should be mentioned that TIMSS does not provide point estimates of mathematics and science test scores instead gives five plausible values of mathematics and science ability. For the sake of simplicity I averaged the five plausible values for each subject and then used the averaged plausible values as the measure of the subject test score. TIMSS 2007 Technical Report highlights that averaging plausible values will not yield suitable estimates of individual student scores (Olson, et al., 2008). However I repeated some of the estimations with plausible values and then compared the point estimates and the standard errors of the population parameter in interest, i.e. ๐3 . In all cases the point estimates were very close to each other and the standard errors were slightly larger which did not affect the statistical significance. In these regression models ๐๐ผ๐๐๐๐ stands for the TIMSS cycle (1999 and 2007), ๐๐ ๐ธ๐ด๐๐๐ ๐ defines the treatment variable which equals to 1 if the subject teacher has four or less years of experience. Observed information regarding teachers, students, classes and schools enters the regression models as control variables (Table 5). The list of control variables was basically constructed within the data limitations. The variables available in TIMSS 1999 and 2007 data sets do not overlap to a significant degree and although some of the necessary variables are available in both data sets the scales of measurement are different. All in all I experimented with every variable which is available in both data sets. The number of missing observations partially had an impact on the selection of control variables. Table 5: List of Control Variables Teacher Class characteristics characteristics Sex Diversity in academic ability Student characteristics Sex Age Age Subject degree Experience Diversity in socioeconomic background Presence of disruptive students Class size Instructional time Parental education # books at home Computer at home Language spoken at home School resources An indicator for school resources Location Following the difference-in-differences analysis with mathematics and science achievement I utilized another aspect of the data structure: The treatment variable offers variation by student. This means that same student may have a mathematics teacher who has four or less years of experience whereas her/his science teacher may have more than four years of experience (or vice versa). Given that both the mathematics and science test scores are observed for each student this structure allows me to employ student fixed effects (Table 6). For that purpose I compiled the mathematics and science data sets and incorporated student fixed effects into the regression models as defined in Table 2. This approach allowed me to relax one of the assumptions which are associated with difference-in-differences approach. After adding student fixed effects into the model I do not have assume that unobserved student and school characteristics have the same distribution across time points and across treatment groups. However I still have to assume that unobserved class characteristics have the same distribution across time points and across treatment groups. Lastly it should be also mentioned that there are other examples which employ very similar identification strategies such as the study of Lavy (2010). Lavy (2010) establishes a causal link between instructional time and student achievement by making use of the within-student variation in the test scores and withinsubject variation in the instructional time. In its essence the identification strategy I make use of is identical to the approach Lavy (2010) uses with one exception that I embed it into a difference-in-differences framework. Although this identification strategy allows me to relax some of the assumptions of the differences-in-differences approach it has also its own shortcomings: First, it leads to a reduction in the sample size and this problem becomes more pronounced in sub-group analyses. Second, it is not possible to decompose the effect into two parts as learning gains in mathematics and learning gains science. Table 6: Fixed effects and difference-in-differences estimations 8. Findings The following table presents the estimated values for the coefficient of interest under different specification as described in Table 4 as well as it also gives sub-group estimates of this coefficient. The analysis has been conducted separately for mathematics and science test scores (Table 7). The results in Table 7 draw attention to several important issues: First, standard errors are very large. Among 50 point estimates of the treatment effect only three of them are statistically different than zero at least at 10 percent significance level. Second, almost all of the point estimates have a negative sign. Third, the point estimates are not stable. In Model 1 without any control variables the point estimates are negative and large; however the addition of teacher, class, student and school characteristics into the regression model rasps this negative treatment effect towards zero. All in all, the difference-in-differences analysis does not provide any information about the possible impact of treatment on student learning because of the very large standard errors the Table 7: Estimation results of difference-in-differences Whole sample Coef Female teacher sample Std Err Adj R² Coef Std Err Adj R² Mathematics Male teacher sample Coef Below median achievers sample Std Err Adj R² Coef Std Err Adj R² Above median achievers sample Coef Std Err Adj R² Model 1 -17.86 [13.94] 0.04 -23.53 [22.02] 0.07 -15.50 [17.44] 0.03 -2.38 [6.32] 0.03 -11.90 [8.50] 0.05 Model 2 -28.15* [16.46] 0.08 -25.76 [20.89] 0.19 -20.10 [21.03] 0.06 -4.34 [7.47] 0.04 -18.43* [10.30] 0.08 Model 3 -27.12 [17.26] 0.10 -10.76 [21.23] 0.26 -28.35 [24.38] 0.09 -2.80 [7.12] 0.05 -16.59 [11.18] 0.10 Model 4 -14.19 [14.02] 0.27 -7.01 [18.09] 0.38 -10.20 [20.20] 0.24 -2.40 [6.82] 0.10 -8.38 [9.29] 0.21 Model 5 -0.61 [13.56] 0.30 6.45 [17.84] 0.40 0.26 0.22 [6.66] 0.11 -0.26 [9.14] 0.23 Obs. 6,750 0.55 2,757 [19.41] 3,993 3,354 3,396 Science -8.46 [6.25] 0.12 0.03 -5.87 [6.94] 0.14 [6.05] 0.04 -4.79 [7.31] 0.18 -2.70 [5.23] 0.10 -2.21 [6.52] 0.27 -4.15 [5.32] 0.11 -1.38 [6.53] 0.27 Model 1 -15.49 [12.30] 0.07 -42.53** [16.51] 0.10 4.36 [17.24] 0.05 -3.41 [6.31] 0.01 Model 2 -17.42 [12.34] 0.09 -28.14 [17.63] 0.12 -2.40 [17.70] 0.08 -5.99 [5.76] Model 3 -17.85 [13.71] 0.14 -15.22 [21.73] 0.18 -12.49 [17.03] 0.17 -4.83 Model 4 -6.89 [10.63] 0.31 -4.98 [17.31] 0.35 -5.00 [13.05] 0.31 Model 5 -6.29 [10.56] 0.31 -11.90 [18.50] 0.36 -2.73 [12.71] 0.31 Obs. 7,085 3,131 3,954 Robust standard errors in brackets clustered at the class level, *** p<0.01, ** p<0.05, * p<0.1 3,536 3,549 treatment effect may be negative, zero or positive. However it also shows that observed class, student and school characteristics do not have the same distribution across time points and across treatment groups given that the point estimates are instable and change signs. Therefore it is very likely that unobserved class, student and school characteristics do not have the same distribution across time points and across treatment groups which is a violation of the assumptions underlying difference-in-differences approach. This may also be a sign of differential assignment of teachers with four or less years of experience to classrooms between 1999 and 2007. In the following I incorporate the student fixed effects into the regression models in order to take into account the factors at student and school levels (Table 8). However teacher and class characteristics vary within student; thus the regressions contain controls for observed teacher and class characteristics. The results in Table 8 are in contrast with the results in Table 7. Generally the standard errors are smaller; more interestingly, with one exception, all of the point estimates of the treatment effect are positive. The point estimates are not sensitive to the addition of the teacher characteristics to the regression; however they are very sensitive to the addition of class characteristics. According to the Model 3, i.e. after controlling for teacher and class characteristics, the impact of the treatment is estimated precisely for the whole, female teacher and below median achievers samples. The standard deviation of the dependent variable in the whole sample is 89. Thus the impact of the policy change on student achievement is around 0.17 standard deviations. However the sub-group analysis exhibits that this impact is channeled mostly through female teachers. Table 8: Estimation results of student fixed effects and difference-in-differences Coef Std Err Adj R² Mathematics & science scores combined Female teacher sample Male teacher sample Below median achievers Above median achievers sample sample Coef Std Err Adj R² Coef Std Err Adj R² Coef Std Err Adj R² Coef Std Err Adj R² Model 1 3.68 [10.62] 0.01 15.10 [12.92] 0.04 7.11 [10.85] 0.03 3.94 [12.59] 0.02 2.94 [8.44] 0.00 Model 2 4.28 [9.36] 0.09 16.07 [12.61] 0.10 8.59 [13.17] 0.14 -0.60 [12.49] 0.20 2.42 [8.13] 0.03 Model 3 14.77** [6.89] 0.22 41.56** [18.32] 0.30 17.63 [14.13] 0.23 20.67*** [5.32] 0.52 6.17 [9.91] 0.06 Whole sample Obs. 4619 612 1166 2959 1675 Robust standard errors in brackets clustered at the class level, *** p<0.01, ** p<0.05, * p<0.1 Table 9: Alternative treatment definitions Coef Std Err Adj R² Math & science scores combined – Model 5 Female sample Male sample Below median achievers Above median achievers sample sample Coef Std Err Adj R² Coef Std Err Adj R² Coef Std Err Adj R² Coef Std Err Adj R² -4.63 [8.18] 0.22 6.64 [19.58] 0.30 0.55 [23.93] 0.23 -14.89** [6.64] 0.51 -0.29 [8.58] 0.06 9-20 years -0.55 [7.01] 0.23 -16.63 [16.99] 0.31 1.53 [10.58] 0.27 -13.69* [8.04] 0.53 6.92 [5.85] 0.06 20+ years -7.34 [8.32] 0.22 4.23 [17.16] 0.30 -33.28** [14.63] 0.24 12.04 [9.98] 0.51 -7.36 [6.14] 0.06 Whole sample 5-8 years Robust standard errors in brackets clustered at the class level, *** p<0.01, ** p<0.05, * p<0.1 The estimated impact of the treatment effect in female teacher sample is 2.8 times higher than the whole sample whereas in male teacher sample the impact is not precisely estimated. Another important inference is that the below median achievers benefit more from the new policy compared to above median achievers. Thus the treatment effect is concentrated on below median achievers. Lastly, the sensitivity of the point estimates to the addition of class characteristics are in line with the findings in Table 7. This may be due to the within-school (between classroom) differential assignment of teachers with 4 or less years of experience to classrooms between 1999 and 2007. The findings in Table 8 provide evidence in favor of a positive and moderately large treatment effect. It may be claimed that within the contextual framework of Turkey, teacher selection with centralized testing leads to higher learning outcomes compared to a recruitment system based solely on subjective evaluation. However, there may be other underlying reasons which can potentially explain the findings in Table 8: For example, there may be a secular increase in the quality of education faculties in Turkey. If this is the case the estimated impact may be due to the quality increase in education faculties instead of the new teacher selection policy. In the same line of thought it can be said that more and more high school students with higher ability opt for education faculties; thus ability distribution of the pool of teacher candidates may shift in time. If these arguments are true I should expect to detect positive estimates of treatment effect for different age brackets of teachers. In order to test these arguments I divided the sample of teachers who have more than four years experience into three parts such that the sizes of the subsamples are equal. These segments are 5-8, 9-20 and 20+ years of experience. These categories defined the alternative treatment variables for each case and I repeated the individual fixed effects exercise with the full model which includes teacher and class characteristics as controls. In Table 9 none of the point estimates are statistically significant and positive; additionally statistically insignificant point estimates are small when compared with the positive point estimates in Table 8. Thus I failed to detect any positive impact of the treatment effect with alternative treatment definitions. Therefore it is more likely that the estimated impact is due to the new selection policy rather than a secular increase in the quality of education faculties or student body. 9. Conclusion These findings are suggestive in their nature and they are not suitable to make causal inferences: Combining individual fixed effects with difference-in-differences allows for a relatively precise estimation of the treatment effect. The remaining problem with this approach is the lack of a complete set of classroom characteristics. The point estimates are sensitive to the classroom characteristics and unobserved classroom characteristics may cause bias on estimates. Although the analysis shows that a downward bias is much more probable. The findings also provide a reasonable explanation for the trend in TIMSS and PISA results. First, since the analyzed period precedes the curriculum reform in Turkey the findings cannot be attributed to the curriculum reform. Second, the findings present a concentrated impact on below median achievers whereas no impact for above median achievers. This is perfectly in line with what we observe in PISA cycles for students in Turkey. The findings are also in accordance with the literature on teacher quality: As mentioned earlier teacher test score is one of most robust indicators of teacher’s effectiveness (Hanushek, 2002, 2003; NCTQ, 2004). Basturk (2008) shows that test scores in college entrance exam are highly predictive for the KPSS test score. Therefore it should be reasonable to interpret success in KPSS as an indication of higher academic ability. 10.Unanswered questions and further research Basic tabulations with TIMSS data point to several important issues: The female share in teaching force is increasing after the introduction of centralized testing. Similarly new teachers are assigned to classrooms which were much more diverse in terms of socioeconomic background and have fewer resources for instruction. The students in these classrooms were more likely to speak Turkish sometimes (but not always), had fewer books at home and their parents were more likely to have less than lower secondary education regions (Table 10). Table 10 provides evidence in favor of the presence of differential assignment of teachers into schools and classrooms. It may be claimed that MONE attempts to ensure a more balanced distribution of teacher assignment across resource rich and poor regions. As mentioned earlier MONE as well as SPO were concerned about the imbalance of teaching force across regions. However these basic tabulations are far from presenting a detailed picture about the change of the distribution of teaching force across resource rich and poor regions/schools/classrooms in Turkey. Thus I plan to extract more information from Household Labor and Budget Surveys of Turkey. These surveys are conducted annually and Household Labor Surveys are available starting from 2000 and Household Budget Surveys are available starting from 2002. Table 10: Differential teacher assignment between 1999 and 2007 1999 2007 TREAT=0 TREAT=1 TREAT=0 TREAT=1 Teacher's sex (%) Female 41 40 35 67 Male 59 60 65 33 Wide range of backgrounds in class (%) not at all 12 6 16 28 a little 49 48 35 20 quite a lot 31 36 38 23 a great deal 8 10 11 29 Resources for math instruction (%) low 32 27 19 31 medium 65 66 72 65 high 4 7 9 5 Language at home Always Turkish 93 84 94 78 Sometimes Turkish 6 14 6 20 Never Turkish 1 2 1 2 # books at home 0-10 20 27 20 37 11-25 36 40 36 41 26-100 29 21 27 15 101-200 9 5 10 5 200+ 6 6 7 2 Parental education University Degree 10 5 10 2 Completed Post-Secondary 21 13 4 2 Completed Secondary 68 80 72 71 Less Than Lower-Secondary 2 2 13 22 Do Not Know 0 0 1 2 These micro data sets are publicly available upon request from TURKSTAT17 and contain detailed regional information and occupational codes. Therefore they allow me to provide more insight concerning the change of teaching force across regions in time. 17 http://www.tuik.gov.tr/UstMenu/body/bilgitalep/mvListe.pdf Another shortcoming of my analysis is that I do not observe whether a teacher is selected via central examination or not. In its ideal case, this analysis should be conducted with a larger student-teacher matched panel data set which contains KPSS test scores for teachers. This data is available in MONE; however it is not publicly available. On the other hand, MONE as well as OSYM usually share aggregated data. Thus I think I will be able to get more data on provincial distribution of teacher assignments and quality of education faculties measured as average test scores of incoming students from MONE and OSYM. There are also methodology related problems in my analysis: Especially TIMSS 1999 Turkey data suffers from substantial missing data mostly due to missing school resource information such as class size and instructional time. As a result I cannot use more than half of the 1999 data in the difference-in-differences regression samples and this problem becomes even more severe with student fixed effects regression samples. For example, the sample size for the female teacher student fixed effect analysis is 612. A basic comparison of complete cases and excluded cases do not exhibit dramatic differences between these groups (Table A1, Table A2); however I plan to solve this problem with multiple imputation techniques. Lastly, the difference-in-differences analysis can be combined with matching techniques. The treatment and control groups can be matched on observable characteristics. Then the difference-in-differences analysis can be repeated on the matched sample. The analysis on the non-matched sample may be problematic because of the lack of overlap of observable characteristics of treatment and control groups. The matching techniques may mitigate this problem. A. Descriptive Tables Table A1: Complete and excluded cases – Difference-in-differences analysis, mathematics regression, 1999 Mathematics score Teachers with 4 or less than 4 years of experience Teacher experience Teahcer's age - under 25 Teahcer's age - 25 to 29 Teahcer's age - 30 to 39 Teahcer's age - 40 to 49 Teahcer's age - 50 to 59 Sex of teacher: Female Sex of teacher: Male Subject degree: No Subject degree: Yes Different academic abilities - not at all Different academic abilities - a little Different academic abilities - some Different academic abilities - a lot Range of background - not at all Range of background - a little Range of background - some Range of background - a lot Disruptive students - not at all Disruptive students - a little Disruptive students - some Disruptive students - a lot Class size Instructional time Sex of student: Female Sex of student: Male Language at home - Always Turkish Language at home - Sometimes Turkish Language at home - Never Turkish # of books at home - 0 -10 # of books at home - 11 -25 # of books at home - 26-100 # of books at home - 101 -200 # of books at home - more than 200 Computer at home: No Computer at home: Yes Age of student Parents' highest education - University degree Parents' highest education - Completed secondary Parents' highest education - Upper secondary Parents' highest education - Lower secondary Parents' highest education - Less than lower secondary Parents' highest education - Don't know School location: Urban School location: Rural Instruction resources - low Instruction resources - medium Instruction resources - high Obs 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 3332 Complete cases - 1999 Std. Mean Dev. Min 429 75 214 18% 0.39 0 13.3 7.5 1 5% 0.21 0 26% 0.44 0 17% 0.38 0 51% 0.50 0 2% 0.13 0 43% 0.50 0 57% 0.50 0 7% 0.25 0 93% 0.25 0 14% 0.34 0 46% 0.50 0 35% 0.48 0 5% 0.22 0 8% 0.27 0 45% 0.50 0 41% 0.49 0 7% 0.25 0 6% 0.23 0 47% 0.50 0 33% 0.47 0 13% 0.34 0 42 14 18 168 33 120 42% 0.49 0 58% 0.49 0 91% 0.28 0 7% 0.26 0 1% 0.11 0 22% 0.41 0 37% 0.48 0 27% 0.44 0 7% 0.26 0 6% 0.24 0 91% 0.29 0 9% 0.29 0 14.2 0.8 10.6 8% 0.27 0 19% 0.40 0 59% 0.49 0 12% 0.32 0 2% 0% 82% 18% 30% 68% 2% 0.13 0.00 0.39 0.39 0.46 0.47 0.13 0 0 0 0 0 0 0 Max 812 1 30 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 90 300 1 1 1 1 1 1 1 1 1 1 1 1 19.3 1 1 1 1 Obs 4509 4369 4369 4476 4476 4476 4476 4476 4476 4476 3638 3638 4229 4229 4229 4229 4412 4412 4412 4412 4364 4364 4364 4364 1826 2960 4502 4502 4250 4250 4250 4396 4396 4396 4396 4396 4416 4416 4504 4202 4202 4202 4202 1 0 1 1 1 1 1 4202 4202 4217 4217 4225 4225 4225 Excluded cases - 1999 Std. Mean Dev. Min 428 82 209 16% 0.36 0 16.2 7.9 1 4% 0.19 0 14% 0.35 0 14% 0.35 0 60% 0.49 0 8% 0.27 0 40% 0.49 0 60% 0.49 0 6% 0.24 0 94% 0.24 0 15% 0.36 0 46% 0.50 0 31% 0.46 0 7% 0.26 0 14% 0.34 0 52% 0.50 0 25% 0.44 0 9% 0.29 0 11% 0.32 0 50% 0.50 0 27% 0.44 0 12% 0.32 0 44 13 5 172 45 120 43% 0.49 0 57% 0.49 0 92% 0.27 0 7% 0.25 0 1% 0.10 0 21% 0.41 0 36% 0.48 0 28% 0.45 0 9% 0.28 0 6% 0.23 0 90% 0.30 0 10% 0.30 0 14.2 0.8 10.4 10% 0.30 0 20% 0.40 0 61% 0.49 0 8% 0.27 0 1% 0% 77% 23% 33% 61% 6% 0.12 0.00 0.42 0.42 0.47 0.49 0.24 0 0 0 0 0 0 0 Max 695 1 31 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 90 300 1 1 1 1 1 1 1 1 1 1 1 1 18.9 1 1 1 1 1 0 1 1 1 1 1 Table A2: Complete and excluded cases – Difference-in-differences analysis, mathematics regression, 2007 Mathematics score Teachers with 4 or less than 4 years of experience Teacher experience Teahcer's age - under 25 Teahcer's age - 25 to 29 Teahcer's age - 30 to 39 Teahcer's age - 40 to 49 Teahcer's age - 50 to 59 Sex of teacher: Female Sex of teacher: Male Subject degree: No Subject degree: Yes Different academic abilities - not at all Different academic abilities - a little Different academic abilities - some Different academic abilities - a lot Range of background - not at all Range of background - a little Range of background - some Range of background - a lot Disruptive students - not at all Disruptive students - a little Disruptive students - some Disruptive students - a lot Class size Instructional time Sex of student: Female Sex of student: Male Language at home - Always Turkish Language at home - Sometimes Turkish Language at home - Never Turkish # of books at home - 0 -10 # of books at home - 11 -25 # of books at home - 26-100 # of books at home - 101 -200 # of books at home - more than 200 Computer at home: No Computer at home: Yes Age of student Parents' highest education - University degree Parents' highest education - Completed secondary Parents' highest education - Upper secondary Parents' highest education - Lower secondary Parents' highest education - Less than lower secondary Parents' highest education - Don't know School location: Urban School location: Rural Instruction resources - low Instruction resources - medium Instruction resources - high Obs 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 3418 Complete cases - 2007 Std. Mean Dev. Min 433 104 179 29% 0.46 0 10.9 9.3 1 14% 0.35 0 35% 0.48 0 17% 0.37 0 20% 0.40 0 14% 0.34 0 40% 0.49 0 60% 0.49 0 3% 0.17 0 97% 0.17 0 13% 0.34 0 20% 0.40 0 28% 0.45 0 38% 0.49 0 19% 0.40 0 29% 0.46 0 35% 0.48 0 16% 0.37 0 5% 0.21 0 29% 0.45 0 31% 0.46 0 35% 0.48 0 34 10 8 161 6 160 46% 0.50 0 54% 0.50 0 89% 0.31 0 10% 0.30 0 1% 0.10 0 25% 0.43 0 38% 0.48 0 23% 0.42 0 9% 0.28 0 5% 0.22 0 57% 0.49 0 43% 0.49 0 14.0 0.7 10.5 7% 0.26 0 3% 0.18 0 20% 0.40 0 51% 0.50 0 17% 1% 74% 26% 21% 74% 5% 0.37 0.11 0.44 0.44 0.41 0.44 0.21 0 0 0 0 0 0 0 Max 802 1 37 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 70 280 1 1 1 1 1 1 1 1 1 1 1 1 18.3 1 1 1 1 Obs 1080 737 737 1080 1080 1080 1080 1080 1080 1080 981 981 1018 1018 1018 1018 809 809 809 809 1004 1004 1004 1004 857 1080 1077 1077 1069 1069 1069 1051 1051 1051 1051 1051 1017 1017 1080 1034 1034 1034 1034 1 1 1 1 1 1 1 1034 1034 998 998 1080 1080 1080 Excluded cases - 2007 Std. Mean Dev. Min 429 108 171 39% 0.49 0 11.1 10.1 1 18% 0.38 0 32% 0.46 0 13% 0.34 0 14% 0.34 0 24% 0.43 0 61% 0.49 0 39% 0.49 0 12% 0.33 0 88% 0.33 0 8% 0.27 0 18% 0.38 0 34% 0.47 0 40% 0.49 0 23% 0.42 0 41% 0.49 0 21% 0.41 0 15% 0.36 0 6% 0.23 0 30% 0.46 0 35% 0.48 0 29% 0.45 0 30 9 9 161 9 160 48% 0.50 0 52% 0.50 0 91% 0.29 0 8% 0.28 0 1% 0.10 0 29% 0.46 0 36% 0.48 0 22% 0.41 0 8% 0.27 0 5% 0.22 0 58% 0.49 0 42% 0.49 0 14.1 0.7 11.1 6% 0.25 0 4% 0.19 0 21% 0.41 0 55% 0.50 0 13% 1% 77% 23% 36% 48% 16% 0.33 0.11 0.42 0.42 0.48 0.50 0.37 0 0 0 0 0 0 0 Max 813 1 31 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 70 240 1 1 1 1 1 1 1 1 1 1 1 1 18.6 1 1 1 1 1 1 1 1 1 1 1 B. Estimation outputs VARIABLES Mathematics - Difference-in-differences Model 1 Model 2 Model 3 coef se coef se coef se Model 4 coef se Model 5 coef se TIMSS 2007 cycle 12.55 [9.05] 22.65** [10.40] 25.90** [11.06] 30.96*** [8.76] 23.86*** [8.42] Treatment -30.25*** [8.82] 17.98 [16.06] 11.55 [16.57] 4.82 [13.33] -0.50 [12.82] TIMSS 2007 cycle * Treatment -17.86 [13.94] -28.15* [16.46] -27.12 [17.26] -14.19 [14.02] -0.61 [13.56] Teacher experience 3.70*** [1.41] 3.04** [1.42] 1.36 [1.03] 0.85 [1.00] Teacher's age 25-29 10.19 [13.21] 6.80 [13.32] 3.34 [10.16] 6.93 [9.72] Teacher's age 30-39 18.28 [20.70] 19.63 [20.46] 6.64 [14.65] 10.41 [13.80] Teacher's age 40-49 -1.05 [26.11] 1.32 [24.94] -1.79 [18.72] 6.86 [17.74] Teacher's age 50-59 -41.92 [34.44] -31.79 [33.35] -21.21 [24.74] -18.37 [24.73] Male teacher -9.03 [9.77] -10.75 [9.84] -3.31 [7.05] 4.70 [6.59] Subject degree 24.74 [19.01] 9.93 [20.01] -7.62 [19.20] -18.08 [18.68] Different academic abilities - a little 23.62 [15.28] 15.63 [11.35] 19.82* [10.92] Different academic abilities - some 20.37 [15.61] 14.02 [11.59] 12.15 [11.43] Different academic abilities - a lot 21.36 [16.87] 18.14 [12.21] 19.14 [12.22] Range of background - a little -9.94 [12.71] -8.06 [9.01] -1.67 [8.71] Range of background - some -1.46 [13.29] -4.32 [9.85] 3.12 [9.39] Range of background - a lot -19.42 [14.82] -16.30 [10.43] -10.67 [9.92] Disruptive students - a little 0.99 [23.55] 6.66 [16.12] 18.57* [10.39] Disruptive students - some 5.48 [23.05] 13.21 [16.10] 26.02** [10.08] Disruptive students - a lot -18.63 [23.96] -14.99 [16.73] -6.02 [10.31] Class size -0.29 [0.34] -0.29 [0.26] -0.50** [0.23] Instructional time 0.21 [0.15] 0.17 [0.11] 0.11 [0.11] Male student 10.53*** [2.75] 11.13*** [2.73] Age of student -10.12*** [1.70] -9.31*** [1.67] Parents' highest education - Completed secondary -53.32*** [7.07] -48.55*** [7.36] Parents' highest education - Upper secondary -61.73*** [6.45] -55.98*** [6.94] Parents' highest education - Lower secondary -90.93*** [7.62] -80.16*** [8.27] Parents' highest education - Less than lower secondary -105.17*** [8.15] -93.36*** [8.68] Parents' highest education - Don't know -151.92*** [14.50] -143.59*** [13.98] Language at home - Sometimes Turkish -29.64*** [5.87] -27.11*** [5.88] Language at home - Never Turkish -47.51*** [13.97] -42.27*** [13.69] # of books at home - 11 -25 24.22*** [3.41] 22.30*** [3.34] # of books at home - 26-100 41.24*** [4.07] 38.62*** [3.93] # of books at home - 101 -200 52.67*** [5.96] 49.17*** [5.86] # of books at home - more than 200 24.41*** [6.41] 24.09*** [6.13] Absence of computer at home -17.21*** [3.84] -13.77*** [3.83] School location - Rural -19.94*** [7.10] Instruction resources - medium 17.59*** [6.44] Instruction resources - high 92.85*** [14.79] Observations 6,750 6,750 Adjusted R-squared 0.04 0.08 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 6,750 0.10 6,750 0.27 6,750 0.30 VARIABLES Mathematics - Female teacher sample - Difference-in-differences Model 1 Model 2 Model 3 coef se coef se coef se Model 4 coef se Model 5 coef se TIMSS 2007 cycle 36.34** [16.19] 47.60*** [13.75] 31.73** [14.08] 28.68** [11.17] 22.15* [12.87] Treatment -34.70***[11.86] 25.64 [19.36] 9.13 [20.99] 4.12 [17.53] -5.80 [16.35] TIMSS 2007 cycle * Treatment -23.53 [22.02] -25.76 [20.89] -10.76 [21.23] -7.01 [18.09] 6.45 [17.84] Teacher experience 2.71* [1.52] 2.47* [1.40] 0.95 [1.01] 0.30 [1.02] Teacher's age 25-29 7.90 [19.66] 2.70 [17.59] 4.04 [12.44] 1.45 [11.17] Teacher's age 30-39 53.88* [31.15] 21.27 [27.64] 12.83 [19.67] 12.54 [17.97] Teacher's age 40-49 43.78 [30.41] 19.24 [30.25] 11.99 [21.22] 18.32 [19.70] Teacher's age 50-59 136.87***[42.57]133.18***[46.71] 106.05*** [32.37] 81.51** [32.24] Subject degree 66.23*** [12.12] 35.91* [18.33] 31.95** [13.46] 14.96 [12.35] Different academic abilities - a little -0.82 [13.82] -4.16 [11.49] 2.83 [10.58] Different academic abilities - some 15.97 [17.04] 8.28 [13.97] 7.05 [12.65] Different academic abilities - a lot 40.96** [17.65] 24.15* [13.02] 21.95* [11.67] Range of background - a little -58.81*** [18.55] -46.33*** [14.39] -35.35** [14.01] Range of background - some -13.12 [16.92] -11.84 [13.80] -2.91 [12.92] Range of background - a lot -65.11*** [20.63] -39.08** [15.64] -24.46 [15.46] Disruptive students - a little 35.66* [20.18] 38.03** [15.69] 36.42*** [13.24] Disruptive students - some 19.17 [22.65] 28.85 [17.76] 32.37** [15.70] Disruptive students - a lot -5.88 [19.82] 0.59 [15.10] 0.52 [12.57] Class size 0.22 [0.47] -0.05 [0.36] -0.46 [0.37] Instructional time 0.01 [0.16] 0.05 [0.13] 0.03 [0.16] Male student 9.63*** [3.53] 9.19** [3.57] Age of student -12.42*** [2.50] -11.82*** [2.43] Parents' highest education - Completed secondary -51.94*** [10.26] -50.48*** [10.89] Parents' highest education - Upper secondary -56.25*** [9.42] -53.82*** [9.95] Parents' highest education - Lower secondary -74.88*** [12.09] -69.66*** [12.41] Parents' highest education - Less than lower secondary -83.50*** [12.34] -76.48*** [12.66] Parents' highest education - Don't know -134.71***[20.88]-129.39***[20.12] Language at home - Sometimes Turkish -37.63*** [8.40] -31.28*** [8.88] Language at home - Never Turkish -27.99 [19.99] -20.88 [19.01] # of books at home - 11 -25 19.74*** [4.80] 19.45*** [4.54] # of books at home - 26-100 40.28*** [6.25] 39.42*** [6.00] # of books at home - 101 -200 48.62*** [8.68] 47.47*** [8.30] # of books at home - more than 200 34.26*** [9.83] 33.35*** [9.30] Absence of computer at home -18.34*** [4.60] -16.24*** [4.69] School location - Rural -28.12*** [8.89] Instruction resources - medium 10.67 [9.38] Instruction resources - high 50.95** [19.93] Observations 2,757 2,757 Adjusted R-squared 0.07 0.19 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 2,757 0.26 2,757 0.38 2,757 0.40 VARIABLES Mathematics - Male teacher sample - Difference-in-differences Model 1 Model 2 Model 3 coef se coef se coef se Model 4 coef se Model 5 coef se TIMSS 2007 cycle -2.03 [11.19] 9.68 [15.28] 21.26 [16.98] 31.62** [13.06] 27.31** [12.56] Treatment -32.67***[11.68] 3.97 [21.72] 12.31 [22.61] 6.31 [18.47] 4.07 [17.97] TIMSS 2007 cycle * Treatment -15.50 [17.44]-20.10[21.03] -28.35 [24.38] -10.20 [20.20] 0.55 [19.41] Teacher experience 3.60* [1.89] 3.65** [1.77] 1.79 [1.32] 1.40 [1.29] Teacher's age 25-29 23.79 [15.91]30.81**[14.78] 22.73 [14.25] 28.11** [13.51] Teacher's age 30-39 11.82 [25.03] 28.99 [24.16] 20.46 [20.03] 25.62 [19.23] Teacher's age 40-49 -11.50[35.22] -2.56 [32.06] 3.52 [26.30] 11.39 [24.77] Teacher's age 50-59 -52.61[42.49] -46.10 [42.26] -23.39 [33.63] -17.50 [33.97] Subject degree -0.09 [14.15] -15.70 [19.21] -32.77* [18.70] -39.82** [19.16] Different academic abilities - a little 33.69 [20.69] 22.96 [15.71] 24.69 [16.14] Different academic abilities - some 30.62 [20.38] 23.68 [15.54] 18.25 [15.91] Different academic abilities - a lot 4.96 [22.46] 9.69 [16.89] 9.96 [18.38] Range of background - a little 13.97 [15.23] 11.76 [11.08] 13.25 [11.01] Range of background - some 9.90 [17.27] 4.68 [13.38] 9.49 [13.43] Range of background - a lot 12.47 [17.73] 1.21 [13.61] 1.65 [13.17] Disruptive students - a little 13.40 [20.35] 10.62 [15.53] 15.93 [11.85] Disruptive students - some 29.13 [19.52] 24.85 [15.22] 29.88*** [10.89] Disruptive students - a lot 12.15 [21.68] 1.15 [16.73] 3.49 [12.58] Class size -0.86** [0.43] -0.67** [0.32] -0.69** [0.31] Instructional time 0.47* [0.26] 0.35* [0.20] 0.27* [0.16] Male student 12.76*** [3.83] 13.50*** [3.79] Age of student -6.80*** [2.18] -6.66*** [2.17] Parents' highest education - Completed secondary -43.73*** [8.43] -42.23*** [8.13] Parents' highest education - Upper secondary -55.84*** [7.95] -53.78*** [7.85] Parents' highest education - Lower secondary -87.02*** [9.62] -80.80*** [9.35] Parents' highest education - Less than lower secondary -102.58***[10.82] -96.26*** [10.38] Parents' highest education - Don't know -149.79***[18.02]-150.02***[17.21] Language at home - Sometimes Turkish -26.53*** [7.90] -26.52*** [7.84] Language at home - Never Turkish -65.42*** [15.85] -62.51*** [14.02] # of books at home - 11 -25 24.09*** [4.20] 21.31*** [4.32] # of books at home - 26-100 35.46*** [4.64] 32.94*** [4.71] # of books at home - 101 -200 49.36*** [7.21] 45.81*** [7.15] # of books at home - more than 200 16.79** [7.70] 15.80** [7.79] Absence of computer at home -12.86** [5.06] -10.42** [5.05] School location - Rural -13.88 [10.75] Instruction resources - medium 21.73*** [7.91] Instruction resources - high 91.88*** [16.13] Observations 3,993 3,993 Adjusted R-squared 0.03 0.06 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 3,993 0.09 3,993 0.24 3,993 0.26 VARIABLES Mathematics - Below median achiever sample - Difference-in-differences Model 1 Model 2 Model 3 Model 4 coef se coef se coef se coef se Model 5 coef se TIMSS 2007 cycle -16.03***[3.25]-13.76*** [3.88] -12.70*** [4.36] -10.39** [4.25] -11.65*** [4.17] Treatment -8.54* [4.40] 0.35 [6.22] -4.46 [6.14] -2.23 [6.03] -3.93 [5.89] TIMSS 2007 cycle * Treatment -2.38 [6.32] -4.34 [7.47] -2.80 [7.12] -2.40 [6.82] 0.22 [6.66] Teacher experience 0.66 [0.41] 0.19 [0.45] 0.02 [0.43] -0.03 [0.44] Teacher's age 25-29 4.07 [6.74] 2.94 [6.17] 2.85 [5.33] 3.76 [5.20] Teacher's age 30-39 1.84 [8.69] 3.56 [7.65] 1.59 [6.98] 2.20 [6.69] Teacher's age 40-49 2.12 [9.71] 7.06 [9.67] 4.64 [9.05] 4.46 [9.18] Teacher's age 50-59 -6.26 [10.26] 1.30 [11.23] 1.29 [10.78] 1.74 [11.75] Male teacher -0.54 [3.76] -1.02 [3.84] -0.23 [3.36] 1.79 [3.25] Subject degree 12.96 [10.77] 9.02 [9.93] 4.45 [10.73] 2.35 [11.37] Different academic abilities - a little 7.44 [5.23] 6.39 [4.53] 8.57* [4.80] Different academic abilities - some 6.57 [5.32] 5.30 [4.61] 5.32 [4.66] Different academic abilities - a lot 4.90 [5.73] 6.14 [4.99] 6.73 [5.11] Range of background - a little -2.41 [4.93] -1.20 [4.07] 0.19 [4.09] Range of background - some 2.35 [4.89] 1.20 [4.08] 2.06 [4.12] Range of background - a lot -4.96 [6.14] -4.06 [5.28] -2.52 [5.08] Disruptive students - a little 0.42 [8.53] 0.87 [7.34] 0.07 [6.83] Disruptive students - some 8.69 [7.95] 8.97 [7.03] 8.81 [6.47] Disruptive students - a lot -2.17 [8.18] -3.62 [7.18] -3.95 [6.55] Class size -0.07 [0.12] -0.08 [0.11] -0.13 [0.11] Instructional time -0.04 [0.06] -0.00 [0.05] 0.00 [0.05] Male student -1.72 [2.28] -1.57 [2.26] Age of student -3.33*** [1.25] -3.21** [1.26] Parents' highest education - Completed secondary 7.25 [7.04] 7.91 [6.82] Parents' highest education - Upper secondary 8.39 [6.17] 8.44 [5.90] Parents' highest education - Lower secondary 1.88 [6.72] 2.59 [6.26] Parents' highest education - Less than lower secondary 0.83 [6.60] 1.89 [6.14] Parents' highest education - Don't know -33.01***[11.40]-32.34***[10.99] Language at home - Sometimes Turkish -14.46*** [3.88] -13.72*** [3.84] Language at home - Never Turkish -22.80** [9.45] -21.22** [9.45] # of books at home - 11 -25 8.55*** [3.11] 8.21*** [3.06] # of books at home - 26-100 11.97*** [3.31] 11.93*** [3.25] # of books at home - 101 -200 13.39** [5.18] 12.94** [5.15] # of books at home - more than 200 2.49 [4.48] 2.99 [4.45] Absence of computer at home -6.90*** [2.46] -5.92** [2.45] School location - Rural -4.67 [3.44] Instruction resources - medium 8.34*** [2.93] Instruction resources - high 31.12*** [9.63] Observations 3,354 3,354 Adjusted R-squared 0.03 0.04 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 3,354 0.05 3,354 0.10 3,354 0.11 VARIABLES Mathematics - Above median achiever sample - Difference-in-differences Model 1 Model 2 Model 3 Model 4 coef se coef se coef se coef se Model 5 coef se TIMSS 2007 cycle 32.48*** [5.98]35.25*** [6.83] 35.10*** [7.20] 34.58*** [6.36] 30.04*** [6.16] Treatment -15.16***[3.97] 13.26 [9.65] 10.86 [9.59] 3.82 [7.48] 2.13 [7.27] TIMSS 2007 cycle * Treatment -11.90 [8.50] -18.43* [10.30] -16.59 [11.18] -8.38 [9.29] -0.26 [9.14] Teacher experience 1.68* [0.91] 1.76** [0.89] 0.75 [0.67] 0.52 [0.64] Teacher's age 25-29 5.97 [8.84] 4.17 [9.72] 0.41 [8.28] 1.26 [7.92] Teacher's age 30-39 17.90 [13.64] 15.76 [14.58] 6.53 [11.31] 7.07 [10.99] Teacher's age 40-49 3.48 [17.14] -1.21 [18.00] -1.48 [13.37] 2.83 [12.06] Teacher's age 50-59 -7.70 [24.74] -13.20 [24.36] -6.65 [18.46] -7.48 [16.75] Male teacher -12.08* [6.99] -9.84 [6.45] -5.09 [4.91] -0.01 [4.82] Subject degree 17.90 [11.74] 10.33 [12.07] 2.35 [10.46] -5.45 [9.78] Different academic abilities - a little 8.80 [10.92] 6.35 [9.00] 8.41 [8.37] Different academic abilities - some 2.78 [11.11] 3.39 [8.94] 2.74 [8.57] Different academic abilities - a lot 10.33 [12.05] 8.86 [9.55] 10.38 [9.19] Range of background - a little -16.16* [9.55] -15.09** [7.45] -11.17 [7.14] Range of background - some -7.81 [9.45] -8.28 [7.53] -3.49 [7.16] Range of background - a lot -18.64* [10.76] -17.83** [7.97] -14.27* [7.42] Disruptive students - a little -4.33 [16.85] 0.13 [12.45] 10.88 [9.46] Disruptive students - some -9.85 [16.61] -1.91 [12.52] 9.13 [9.21] Disruptive students - a lot -12.29 [16.86] -9.38 [12.61] -2.19 [9.13] Class size -0.05 [0.22] -0.11 [0.17] -0.25 [0.17] Instructional time 0.20 [0.13] 0.15 [0.10] 0.12 [0.10] Male student 7.22** [2.94] 7.69*** [2.94] Age of student -2.41 [1.58] -2.24 [1.54] Parents' highest education - Completed secondary -30.04*** [6.94] -29.35*** [7.13] Parents' highest education - Upper secondary -39.78*** [6.01] -37.93*** [6.33] Parents' highest education - Lower secondary -55.28*** [6.99] -50.36*** [7.41] Parents' highest education - Less than lower secondary -60.10*** [7.37] -55.16*** [7.75] Parents' highest education - Don't know -76.10***[14.77]-78.87***[15.25] Language at home - Sometimes Turkish -0.67 [5.13] 0.70 [5.10] Language at home - Never Turkish -2.87 [17.08] -1.44 [17.37] # of books at home - 11 -25 14.97*** [3.36] 14.31*** [3.44] # of books at home - 26-100 21.77*** [3.78] 20.75*** [3.87] # of books at home - 101 -200 32.75*** [5.73] 31.51*** [5.61] # of books at home - more than 200 23.67*** [5.96] 22.83*** [5.73] Absence of computer at home -8.69** [3.88] -7.55* [3.86] School location - Rural -13.46*** [5.15] Instruction resources - medium 7.30 [5.09] Instruction resources - high 42.31*** [10.98] Observations 3,396 3,396 Adjusted R-squared 0.05 0.08 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 3,396 0.10 3,396 0.21 3,396 0.23 VARIABLES Science - Difference-in-differences Model 1 Model 2 Model 3 coef se coef se coef se Model 4 coef se Model 5 coef se TIMSS 2007 cycle 34.88*** [7.81] 39.36*** [7.13] 52.30*** [9.69] 51.92*** [7.34] 48.20*** [7.26] Treatment -31.95*** [8.58] -27.12** [13.02] -16.24 [13.56] -16.95 [10.70] -14.43 [11.35] TIMSS 2007 cycle * Treatment -15.49 [12.30] -17.42 [12.34] -17.85 [13.71] -6.89 [10.63] -6.29 [10.56] Teacher experience 2.12** [0.88] 2.41*** [0.79] 0.78 [0.61] 0.53 [0.62] Teacher's age 25-29 14.34 [10.86] 16.53 [12.96] 7.84 [8.95] 8.61 [9.33] Teacher's age 30-39 -16.72 [14.67] -10.46 [15.55] -10.92 [10.56] -9.14 [11.50] Teacher's age 40-49 -13.06 [17.31] -18.18 [17.87] -8.10 [12.23] -1.93 [12.81] Teacher's age 50-59 -46.36* [26.02] -38.98 [24.90] -22.26 [17.14] -18.77 [17.54] Male teacher -1.13 [7.22] -6.21 [6.82] -0.95 [5.00] -0.51 [4.92] Subject degree -3.78 [8.86] -0.45 [8.30] -0.46 [6.08] -0.68 [6.00] Different academic abilities - a little -16.47 [11.49] -15.87* [8.46] -16.24* [8.28] Different academic abilities - some -27.87** [11.33] -20.48** [8.86] -19.24** [8.83] Different academic abilities - a lot -16.86 [12.27] -12.41 [9.54] -12.70 [9.73] Range of background - a little -21.98** [9.82] -11.02* [6.57] -7.89 [6.81] Range of background - some -30.30***[11.15] -16.68** [7.31] -11.78 [7.38] Range of background - a lot -37.82***[11.96] -23.51*** [8.89] -19.95** [9.08] Disruptive students - a little -14.36 [16.43] -7.00 [13.50] -3.07 [13.97] Disruptive students - some -29.67* [16.77] -20.26 [13.78] -17.69 [14.19] Disruptive students - a lot -23.05 [17.91] -13.07 [14.66] -11.57 [15.16] Class size 0.27 [0.30] -0.05 [0.21] -0.10 [0.22] Instructional time 0.33*** [0.11] 0.20*** [0.07] 0.16** [0.08] Male student 7.11*** [2.53] 7.35*** [2.49] Age of student -8.38*** [1.55] -8.27*** [1.54] Parents' highest education - Completed secondary -36.60*** [5.30] -35.52*** [5.52] Parents' highest education - Upper secondary -49.54*** [5.02] -48.49*** [5.27] Parents' highest education - Lower secondary -73.06*** [5.86] -70.74*** [6.04] Parents' highest education - Less than lower secondary -83.01*** [6.32] -80.38*** [6.54] Parents' highest education - Don't know -121.91***[13.11]-119.68***[12.93] Language at home - Sometimes Turkish -37.04*** [4.52] -36.41*** [4.62] Language at home - Never Turkish -49.47*** [9.87] -48.72*** [9.70] # of books at home - 11 -25 19.56*** [2.93] 18.75*** [2.86] # of books at home - 26-100 36.81*** [3.83] 35.61*** [3.77] # of books at home - 101 -200 39.09*** [4.73] 37.58*** [4.69] # of books at home - more than 200 20.24*** [5.74] 19.60*** [5.65] Absence of computer at home -15.30*** [3.11] -14.34*** [3.12] School location - Rural -7.73 [6.23] Instruction resources - medium 4.45 [5.79] Instruction resources - high 27.58*** [9.70] Observations 7,085 7,085 Adjusted R-squared 0.07 0.09 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 7,085 0.14 7,085 0.31 7,085 0.31 VARIABLES Science - Female teacher sample - Difference-in-differences Model 1 Model 2 Model 3 coef se coef se coef se Model 4 coef se Model 5 coef se TIMSS 2007 cycle 53.75***[11.81]53.07***[10.98] 57.95*** [16.13] 53.81*** [10.56] 49.39*** [10.88] Treatment -12.39 [9.55] -13.97 [16.86] -6.43 [21.74] -10.06 [17.72] 7.32 [20.02] TIMSS 2007 cycle * Treatment -42.53** [16.51] -28.14 [17.63] -15.22 [21.73] -4.98 [17.31] -11.90 [18.50] Teacher experience 3.25* [1.68] 4.71*** [1.59] 2.97** [1.29] 2.86** [1.22] Teacher's age 25-29 33.92** [13.35] 30.54* [17.17] 9.61 [13.55] 9.39 [14.56] Teacher's age 30-39 -0.06 [21.80] 0.83 [26.24] -15.42 [17.94] -13.10 [19.06] Teacher's age 40-49 -9.83 [28.92] -38.51 [31.77] -34.71 [22.64] -23.46 [23.80] Teacher's age 50-59 -34.70 [56.16] -49.34 [60.15] -60.07 [42.76] -52.99 [41.62] Subject degree -8.22 [13.21] -13.55 [13.55] -12.88 [10.20] -12.13 [9.67] Different academic abilities - a little -22.66 [17.09] -18.31 [13.60] -18.80 [12.46] Different academic abilities - some 3.55 [19.22] 2.39 [16.48] 1.52 [16.04] Different academic abilities - a lot -10.05 [17.54] -7.37 [14.68] -11.26 [15.64] Range of background - a little -30.78 [19.52] -11.93 [14.41] -7.60 [12.23] Range of background - some -42.22* [23.66] -23.99 [16.32] -14.15 [14.92] Range of background - a lot -30.33 [21.75] -16.55 [16.33] -14.07 [14.51] Disruptive students - a little -62.26** [24.44] -49.34** [22.37] -50.39** [20.97] Disruptive students - some -77.16***[26.60] -59.57** [23.81] -56.17** [22.48] Disruptive students - a lot -74.47***[27.01] -52.53** [24.16] -53.92** [23.16] Class size -0.11 [0.51] -0.48 [0.38] -0.90** [0.40] Instructional time 0.43*** [0.16] 0.26* [0.13] 0.22 [0.16] Male student 1.14 [3.76] 1.22 [3.63] Age of student -8.15*** [2.45] -8.19*** [2.42] Parents' highest education - Completed secondary -30.50*** [7.91] -24.84*** [8.04] Parents' highest education - Upper secondary -46.67*** [6.93] -41.83*** [7.30] Parents' highest education - Lower secondary -67.67*** [8.61] -60.74*** [8.74] Parents' highest education - Less than lower secondary -77.59*** [9.28] -70.58*** [9.42] Parents' highest education - Don't know -109.12***[19.58]-100.56***[18.48] Language at home - Sometimes Turkish -28.78*** [6.13] -27.54*** [6.24] Language at home - Never Turkish -38.11*** [13.32] -35.02*** [12.54] # of books at home - 11 -25 21.77*** [4.29] 20.82*** [4.29] # of books at home - 26-100 45.44*** [5.39] 43.70*** [5.36] # of books at home - 101 -200 46.25*** [7.40] 44.59*** [7.35] # of books at home - more than 200 28.04*** [8.44] 26.20*** [7.86] Absence of computer at home -19.08*** [4.54] -16.95*** [4.50] School location - Rural -15.72 [10.32] Instruction resources - medium 12.45 [8.91] Instruction resources - high 48.47*** [12.47] Observations 3,131 3,131 Adjusted R-squared 0.10 0.12 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 3,131 0.18 3,131 0.35 3,131 0.36 VARIABLES Science - Male teacher sample - Difference-in-differences Model 1 Model 2 Model 3 coef se coef se coef se Model 4 coef se Model 5 coef se TIMSS 2007 cycle 22.65** [10.11] 29.47*** [10.02] 49.20*** [11.82] 50.95*** [9.33] 48.99*** [9.27] Treatment -44.33***[13.10]-51.57***[19.66] -23.62 [18.52] -20.40 [14.59] -25.72* [14.53] TIMSS 2007 cycle * Treatment 4.36 [17.24] -2.40 [17.70] -12.49 [17.03] -5.00 [13.05] -2.73 [12.71] Teacher experience 1.26 [0.83] 2.12** [0.83] 0.76 [0.66] 0.75 [0.65] Teacher's age 25-29 -7.83 [13.29] -5.34 [13.33] -0.08 [10.84] -4.63 [10.21] Teacher's age 30-39 -47.60***[16.94] -27.85* [16.35] -17.55 [12.70] -24.07* [12.21] Teacher's age 40-49 -31.34* [17.58] -35.74* [18.72] -18.23 [14.36] -23.62* [13.56] Teacher's age 50-59 -60.29** [24.96] -51.64** [24.08] -26.10 [17.93] -31.57* [17.47] Subject degree -0.34 [12.65] 8.54 [9.37] 8.32 [6.53] 6.49 [6.55] Different academic abilities - a little 2.11 [12.17] -0.14 [9.11] 0.96 [8.98] Different academic abilities - some -36.79***[11.82] -25.09*** [8.72] -22.86** [9.23] Different academic abilities - a lot -23.70* [13.96] -14.89 [9.37] -15.61 [10.01] Range of background - a little -19.35* [11.66] -12.16 [7.71] -6.76 [9.24] Range of background - some -25.37** [12.77] -14.39 [8.95] -10.69 [9.78] Range of background - a lot -52.14***[12.73] -35.55*** [9.84] -29.54*** [10.82] Disruptive students - a little 4.73 [15.09] 10.22 [9.50] 17.60** [8.23] Disruptive students - some -14.37 [16.51] -5.85 [10.44] -0.73 [8.97] Disruptive students - a lot 5.21 [16.34] 9.13 [11.15] 16.61 [10.14] Class size 0.46 [0.29] 0.13 [0.22] 0.16 [0.22] Instructional time 0.30* [0.16] 0.21* [0.11] 0.15 [0.11] Male student 12.76*** [3.34] 12.93*** [3.36] Age of student -8.72*** [2.05] -8.52*** [2.06] Parents' highest education - Completed secondary -39.08*** [7.21] -39.08*** [7.08] Parents' highest education - Upper secondary -50.71*** [7.27] -51.39*** [7.16] Parents' highest education - Lower secondary -74.58*** [7.97] -74.57*** [7.89] Parents' highest education - Less than lower secondary -83.97*** [8.83] -84.11*** [8.90] Parents' highest education - Don't know -123.96***[15.17]-123.93***[14.72] Language at home - Sometimes Turkish -36.89*** [5.87] -36.93*** [5.78] Language at home - Never Turkish -51.70*** [11.56] -51.96*** [11.55] # of books at home - 11 -25 15.19*** [3.64] 15.20*** [3.57] # of books at home - 26-100 27.02*** [4.44] 27.33*** [4.45] # of books at home - 101 -200 31.87*** [5.54] 31.63*** [5.33] # of books at home - more than 200 10.62 [7.52] 11.04 [7.55] Absence of computer at home -8.41** [3.95] -8.43** [3.98] School location - Rural 5.33 [6.65] Instruction resources - medium -1.88 [6.42] Instruction resources - high 24.35* [12.73] Observations 3,954 3,954 Adjusted R-squared 0.05 0.08 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 3,954 0.17 3,954 0.31 3,954 0.31 VARIABLES Science - Below median achiever sample - Difference-in-differences Model 1 Model 2 Model 3 coef se coef se coef se TIMSS 2007 cycle 6.19* Treatment -5.49 TIMSS 2007 cycle * Treatment -3.41 Teacher experience Teacher's age 25-29 Teacher's age 30-39 Teacher's age 40-49 Teacher's age 50-59 Male teacher Subject degree Different academic abilities - a little Different academic abilities - some Different academic abilities - a lot Range of background - a little Range of background - some Range of background - a lot Disruptive students - a little Disruptive students - some Disruptive students - a lot Class size Instructional time Male student Age of student Parents' highest education - Completed secondary Parents' highest education - Upper secondary Parents' highest education - Lower secondary Parents' highest education - Less than lower secondary Parents' highest education - Don't know Language at home - Sometimes Turkish Language at home - Never Turkish # of books at home - 11 -25 # of books at home - 26-100 # of books at home - 101 -200 # of books at home - more than 200 Absence of computer at home School location - Rural Instruction resources - medium Instruction resources - high [3.37] [4.44] [6.31] Model 4 coef se 9.80*** [2.82] 8.13* [4.78] 14.80*** [4.17] -8.95 [5.95] -8.46 [5.99] -7.76 [5.32] [5.76] [6.05] [5.23] -5.99 -4.83 -2.70 0.52 [0.41] 0.56 [0.39] 0.18 [0.36] 8.08 [5.81] 9.18 [6.43] 5.62 [4.99] -5.75 [7.98] -4.03 [7.80] -5.77 [5.96] -6.05 [9.59] -8.18 [9.51] -7.45 [7.80] -26.73** [12.82] -24.66* [12.62] -20.08* [10.23] 7.20** [3.06] 7.45** [3.02] 7.74*** [2.64] 1.08 [3.17] 1.34 [3.04] 2.49 [2.62] -7.53* [4.32] -8.41** [3.93] -7.73* [4.17] -7.79** [3.87] -4.17 [4.70] -5.52 [4.41] -0.04 [4.30] 2.84 [3.71] -9.46** [4.65] -4.19 [3.92] -9.33* [4.81] -5.97 [4.20] 2.12 [5.52] 4.10 [4.82] 2.65 [5.83] 3.32 [5.14] 3.19 [6.08] 6.01 [5.23] 0.15 [0.14] 0.07 [0.11] -0.02 [0.08] 0.03 [0.06] -1.81 [2.11] -3.38*** [1.13] 2.66 [5.53] -1.84 [4.78] -11.78** [5.25] -12.69** [5.60] -40.91*** [14.04] -16.12*** [2.76] -28.30*** [6.14] 6.27** [2.88] 9.94*** [3.26] 7.11* [4.25] -7.46 [5.63] -7.07*** [2.43] Observations 3,536 3,536 Adjusted R-squared 0.01 0.03 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 3,536 0.04 3,536 0.10 Model 5 coef se 16.69*** [3.87] -3.42 [5.64] [5.32] -4.15 0.04 [0.35] 6.70 [4.77] -3.54 [5.88] -3.80 [7.42] -17.97* [10.11] 7.64*** [2.52] 3.31 [2.46] -9.15** [4.07] -8.44** [3.98] -7.39 [4.82] 3.89 [3.64] -0.95 [3.79] -5.00 [4.11] 4.44 [5.02] 2.04 [5.20] 4.69 [5.60] -0.01 [0.10] 0.09 [0.06] -1.82 [2.09] -3.45*** [1.13] 2.88 [5.46] -1.49 [4.64] -10.30** [5.06] -11.03** [5.43] -39.27*** [13.70] -15.92*** [2.72] -27.27*** [6.12] 5.61* [2.85] 9.38*** [3.20] 5.78 [4.14] -7.99 [5.56] -5.89** [2.46] -8.09*** [3.03] 2.33 [2.79] 21.23*** [4.51] 3,536 0.11 VARIABLES Science - Above median achiever sample - Difference-in-differences Model 1 Model 2 Model 3 coef se coef se coef se Model 4 coef se Model 5 coef se TIMSS 2007 cycle 44.34*** [4.63]42.79*** [4.28] 53.17*** [5.26] 51.64*** [5.05] 50.14*** [5.22] Treatment -21.54***[4.03] -14.39* [7.57] -7.25 [7.79] -7.27 [6.55] -5.74 [6.70] TIMSS 2007 cycle * Treatment -8.46 [6.25] -5.87 [6.94] -4.79 [7.31] -2.21 [6.52] -1.38 [6.53] Teacher experience 1.48*** [0.52] 1.70*** [0.48] 0.87** [0.41] 0.76* [0.41] Teacher's age 25-29 9.94* [5.57] 10.70 [6.70] 9.54* [5.47] 9.99* [5.41] Teacher's age 30-39 -2.84 [8.29] 0.05 [8.16] 1.63 [6.68] 2.85 [7.09] Teacher's age 40-49 -5.96 [9.82] -8.11 [10.01] -0.33 [8.36] 2.50 [8.48] Teacher's age 50-59 -16.45 [13.12] -16.84 [12.76] -8.18 [10.62] -6.01 [10.49] Male teacher -7.71* [4.11] -10.72*** [3.96] -6.81** [3.24] -6.55** [3.25] Subject degree -2.80 [5.57] -3.37 [4.91] -4.84 [3.74] -5.07 [3.76] Different academic abilities - a little -6.93 [7.79] -7.40 [6.44] -7.54 [6.30] Different academic abilities - some -11.59 [7.46] -8.52 [6.43] -8.28 [6.41] Different academic abilities - a lot -12.92 [8.24] -9.50 [6.95] -9.48 [6.96] Range of background - a little -10.68* [6.29] -7.65 [4.79] -6.81 [4.78] Range of background - some -12.22* [7.12] -10.18* [5.27] -9.06* [5.14] Range of background - a lot -17.54** [7.43] -12.87** [6.29] -12.47** [6.30] Disruptive students - a little -10.31 [12.42] -9.57 [11.22] -8.04 [11.58] Disruptive students - some -15.84 [12.54] -13.30 [11.30] -12.24 [11.54] Disruptive students - a lot -10.28 [13.33] -9.25 [12.10] -8.60 [12.35] Class size 0.15 [0.16] 0.01 [0.14] -0.02 [0.14] Instructional time 0.26*** [0.06] 0.16*** [0.06] 0.15*** [0.05] Male student 6.79*** [2.27] 6.89*** [2.27] Age of student -1.58 [1.50] -1.49 [1.49] Parents' highest education - Completed secondary -22.67*** [5.11] -22.49*** [5.21] Parents' highest education - Upper secondary -31.81*** [4.51] -31.51*** [4.64] Parents' highest education - Lower secondary -41.49*** [5.11] -40.90*** [5.28] Parents' highest education - Less than lower secondary -50.76*** [5.27] -50.17*** [5.42] Parents' highest education - Don't know -62.91***[15.56]-62.66***[15.66] Language at home - Sometimes Turkish -5.15 [4.83] -4.52 [4.82] Language at home - Never Turkish -16.57*** [6.22] -17.17*** [6.21] # of books at home - 11 -25 11.33*** [2.84] 11.09*** [2.86] # of books at home - 26-100 14.89*** [2.97] 14.42*** [3.02] # of books at home - 101 -200 18.06*** [4.39] 17.64*** [4.40] # of books at home - more than 200 16.63*** [4.88] 16.38*** [4.88] Absence of computer at home -5.42* [2.90] -5.26* [2.89] School location - Rural -4.73 [4.24] Instruction resources - medium 1.00 [3.98] Instruction resources - high 5.76 [6.80] Observations 3,549 3,549 Adjusted R-squared 0.12 0.14 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 3,549 0.18 3,549 0.27 3,549 0.27 VARIABLES Difference-in-differences and student fixed effects Model 1 Model 2 coef se coef se TIMSS 2007 cycle TIMSS 2007 cycle * Treatment Teacher experience Teacher's age 25-29 Teacher's age 30-39 Teacher's age 40-49 Teacher's age 50-59 Male teacher Subject degree Class size Instructional time Instruction resources - medium Instruction resources - high Different academic abilities - a little Different academic abilities - some Different academic abilities - a lot Range of background - a little Range of background - some Range of background - a lot Disruptive students - a little Disruptive students - some Disruptive students - a lot -11.21 [7.80] 3.68 [10.62] 6.88 [7.40] [9.36] 4.28 1.05** [0.48] 9.16 [9.10] 24.89** [9.72] 12.34 [11.92] -0.46 [15.01] -7.26** [3.50] -8.21** [4.00] Number of observations 4,916 4,916 Adjusted R-squared 0.01 0.09 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 Model 3 coef se -9.33 [6.78] 14.77** [6.89] 0.06 [0.35] 7.09 [5.05] 11.24* [5.84] 13.83** [6.71] 8.76 [9.43] -3.73 [2.53] 0.84 [3.06] -0.08 [0.22] -0.48*** [0.05] 5.24 [4.56] 44.80*** [10.70] 2.23 [4.98] -1.21 [4.74] 1.60 [4.66] 4.27 [3.74] 7.57* [4.33] 3.80 [4.97] 0.67 [7.86] 0.87 [7.51] -4.89 [7.73] 4,916 0.22 Difference-in-differences and student fixed effects - Female teacher sample Model 1 Model 2 Model 3 VARIABLES coef se coef se coef se TIMSS 2007 cycle TIMSS 2007 cycle * Treatment Teacher experience Teacher's age 25-29 Teacher's age 30-39 Teacher's age 40-49 Teacher's age 50-59 Subject degree Class size Instructional time Instruction resources - medium Different academic abilities - a little Different academic abilities - some Different academic abilities - a lot Range of background - a little Range of background - some Range of background - a lot Disruptive students - a little Disruptive students - some Disruptive students - a lot -32.13*** [0.00] -12.17 [9.66] -35.48** [14.43] [12.92] 16.07 [12.61] 41.56** [18.32] 15.10 1.07 [0.88] 0.24 [0.73] -7.71 [19.91] 0.30 [11.72] 9.03 [21.81] -5.86 [15.12] -0.96 [22.65] 10.72 [18.84] 14.96 [26.05] 55.19** [21.44] 6.35 [8.13] 12.80** [5.97] 0.43* [0.24] -0.64*** [0.14] 31.50** [14.79] -2.11 [9.63] -3.48 [10.65] -4.48 [6.60] -10.47 [9.80] -6.90 [9.77] -10.73 [9.34] 15.86 [10.04] 10.79 [11.63] 8.24 [14.13] Observations 612 612 Adjusted R-squared 0.04 0.10 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 612 0.30 Difference-in-differences and student fixed effects - Male teacher sample Model 1 Model 2 Model 3 VARIABLES coef se coef se coef se TIMSS 2007 cycle TIMSS 2007 cycle * Treatment Teacher experience Teacher's age 25-29 Teacher's age 30-39 Teacher's age 40-49 Teacher's age 50-59 Subject degree Class size Instructional time Instruction resources - medium Instruction resources - high Different academic abilities - a little Different academic abilities - some Different academic abilities - a lot Range of background - a little Range of background - some Range of background - a lot Disruptive students - a little Disruptive students - some Disruptive students - a lot -24.94 [.] 7.11 [10.85] 10.91 8.59 0.93 23.43* 47.15*** 31.10* 24.40 -7.71 [9.76] [13.17] [0.71] [13.82] [13.92] [17.95] [21.35] [8.22] Observations 1,166 1,166 Adjusted R-squared 0.03 0.14 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 -20.29 17.63 -0.29 6.11 18.31 18.78 15.97 -0.40 0.02 -0.38*** -4.53 32.43* -4.87 -7.00 -12.29 8.69 10.74 1.65 7.60 9.36 9.31 [17.07] [14.13] [0.75] [12.17] [12.48] [12.90] [17.06] [6.60] [0.50] [0.08] [7.03] [17.23] [10.60] [11.22] [8.83] [6.89] [10.83] [13.21] [14.69] [13.73] [16.30] 1,166 0.23 Difference-in-differences and student fixed effects - Below median achiever sample Model 1 Model 2 Model 3 VARIABLES coef se coef se coef se TIMSS 2007 cycle TIMSS 2007 cycle * Treatment Teacher experience Teacher's age 25-29 Teacher's age 30-39 Teacher's age 40-49 Teacher's age 50-59 Male teacher Subject degree Class size Instructional time Instruction resources - medium Instruction resources - high Different academic abilities - a little Different academic abilities - some Different academic abilities - a lot Range of background - a little Range of background - some Range of background - a lot Disruptive students - a little Disruptive students - some Disruptive students - a lot -15.55** [7.85] [12.59] 3.94 16.23 -0.60 2.08*** 3.25 27.26** -0.39 -22.03 -7.47 -14.58** [10.98] -18.57*** [4.78] [12.49] 20.67*** [5.32] [0.77] 0.19 [0.31] [11.13] 2.06 [3.95] [12.58] 4.75 [5.25] [16.90] 3.70 [6.51] [21.57] -2.07 [8.61] [5.18] -0.67 [2.45] [5.78] 0.87 [2.79] -0.09 [0.32] -0.80*** [0.06] 1.06 [4.47] 150.53*** [9.17] -0.02 [4.47] -2.92 [3.88] -0.66 [4.11] 4.75 [3.38] 4.66 [3.47] 0.85 [3.61] 1.29 [6.60] 1.73 [6.30] -1.90 [6.62] Observations 2,959 2,959 Adjusted R-squared 0.02 0.20 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 2,959 0.52 Difference-in-differences and student fixed effects - Above median achiever sample Model 1 Model 2 Model 3 VARIABLES coef se coef se coef se TIMSS 2007 cycle TIMSS 2007 cycle * Treatment Teacher experience Teacher's age 25-29 Teacher's age 30-39 Teacher's age 40-49 Teacher's age 50-59 Male teacher Subject degree Class size Instructional time Instruction resources - medium Instruction resources - high Different academic abilities - a little Different academic abilities - some Different academic abilities - a lot Range of background - a little Range of background - some Range of background - a lot Disruptive students - a little Disruptive students - some Disruptive students - a lot -4.42 2.94 [6.98] [8.44] 2.59 2.42 0.02 13.76*** 18.82*** 20.22*** 18.12* -7.97*** -0.59 [6.71] [8.13] [0.31] [5.18] [6.05] [7.12] [9.74] [3.02] [3.30] Observations 1,675 1,675 Adjusted R-squared 0.00 0.03 Standard errors clustered at the class level; *** p<0.01, ** p<0.05, * p<0.1 -1.77 6.17 -0.17 14.01*** 14.46** 19.76*** 19.38** -6.27** 3.43 -0.15 -0.17*** 8.63* 7.04 -1.08 -3.50 1.08 0.57 3.12 1.59 -5.50 -5.41 -4.52 1,675 0.06 [9.16] [9.91] [0.32] [4.69] [5.74] [5.96] [8.55] [2.99] [3.44] [0.19] [0.05] [4.98] [11.28] [4.09] [4.24] [4.07] [3.04] [3.89] [5.45] [7.76] [7.68] [7.80] References Aaronson, D., Barrow, L., & Sander, W. 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