SCHOOL START AGE AND
HYPERACTIVITY IN CANADIAN
CHILDREN
Kelly Chen, Nicole Fortin, Philip Oreopoulos and
Shelley Phipps
2


This research is being conducted as part of the
Canadian Institute for Advanced Research (CIFAR)
Programme on Social Interactions, Identity and
Well-Being
We thank CIFAR for funding support and Heather
Hobson of the Atlantic Research Data Centre for
vetting our output
Motivation
3



Attention-deficit/hyperactivity disorder (ADHD) is the
most commonly diagnosed behavioural disorder among
young children in many countries (Elder, 2010; Faraone,
et al., 2003; Skounti et al., 2007)
Secular trends hard to identify given changes in
diagnostic practices, but dramatic increases apparent
over past 40 years (Perrin et al., 2007)
Current estimates suggest worldwide ADHD prevalence
between 4 and 10 percent (Faraone, et al., 2003;
Skounti et al., 2007; Spencer et al., 2007)
Consequences of ADHD in Educational
Context
4
Score lower on math/reading tests
 More likely to repeat a grade
 More behavioural problems at school
(Currie and Stabile, 2006; Loe and Feldman, 2007)

** These present even for children with some
symptoms of hyperactivity, even if not diagnosed or
at clinical levels
School Start Age and Hyperactivity
5

Elder (2010) presents evidence that children who are
young within grade at school are more frequently
diagnosed with ADHD



8.4 percent of those born in the month prior to state cut-off
for kindergarten eligibility compared to 5.1 percent for
those born in the month after
Teacher assessments of symptoms had strong
association with relative child age; parent assessments
only a weak association
Sciotto et al., 2004 find that teachers are more likely to
refer boys for ADHD
Misdiagnosis not the Whole Story?
6


Children who are young in class may feel
frustration, be more tired, like school less, be less
engaged and so become restless or inattentive?
We’ll look at impact of school start age on
symptoms of hyperactivity well below normal
‘clinical’ levels, which can still connect to poorer
educational outcomes (Currie and Stabile, 2006;
Chen et al., 2011)
Research Questions
7



Are Canadian children who are young relative to
their class-mates more likely to exhibit symptoms of
hyperactivity than their classmates?
If so, are there gender differences in the extent to
which this is true?
Is there an impact of being young in class even
controlling for pre-school hyperactive symptoms?
School Entering Rules in Canada
8

Across provinces, children are admitted to school
once a year, with eligibility determined by a single
cut-off date
 Kindergarten
not compulsory, but is ‘normal’
 Compliance rates very high (over 95% of children in
‘correct grade’ in K through 3

Each province (school board, in AB/SK) has the
flexibility to set school entry dates
 Range
2004
from early September to March during1987-
Cut-Off Dates for School Entry
Sep. 1
Sep. 30 Dec. 1
Dec. 31
Last Day of Mar. 1
Feb.
AB
QC
BC
SK
MB(97-04)
ON
NB
NL
AB
Calgary NS
School
District
MB(8796)
AB
9
Lethbridge
Red Deer
Lloydminster
Grande Prairie
Wetaskiwin
AB
Medicine Edmonton
Hat School School
District
District
Two Research Strategies
10

“Regression Discontinuity”
 Compare
children within provinces who are born just
before or just after school start date (e.g., Nov/Dec
versus Jan/Feb babies, when Dec 31 is cut-off)

“Difference in Difference”
 Compare
children of exactly the same age in months
living in provinces with different start dates so that one
may be ‘youngest in class’ while another is ‘oldest in
class’ (e.g., Nov babies who are ‘young’ with Dec 31
cut-off but ‘old’ with a September 30 cut-off)
Data
11



Statistics Canada’s National Longitudinal Survey of
Children and Youth (NSLCY)
First cycle begins in 94/95 with data collection
occurring at two year intervals
Pool data from cycles 1 through 8, 1994 through
2008
Basic Analytical Sample
12
 Children
aged 4 -9 years
 In Kindergarten through Grade 3
 Who attended public (or publically funded)
schools
 With parent report of province of residence
when 4/5 years old and have not moved
inter-provincially since
Hyperactivity Index
13

“How often would say this child …”
“Can’t sit still or is restless”
 “Is easily distracted, has trouble sticking to an activity”
 “Can’t concentrate, can’t pay attention for long”
 “Is impulsive, acts without thinking”
 “Has difficulty waiting for his turn in games or groups”
 “Cannot settle to anything for more than a few minutes”
 “Is inattentive”
1= Never or not true; 2= Sometimes or somewhat true;
3=Often or very true
Score ranges from 0 to 14

Research Strategy I.
14

Regression Discontinuity
Hyperi = α+ τ Youngi + γ f(bdi-ci) + β1 Province i + β2
Cycle i + β3 Grade i + λ Xi + ε i

Compare children within a province and grade who
are born ‘just before’ and ‘just after’ the legal cutoff date
Illustration of RD approach
15
0
1
2
3
4
5
6
PMK Assessed Hyperactivity Score
-10
0
15-Day Blocks of Age Relative to the Cut-Off Date
10
Table 1. Regression Discontinuity Estimates of the Effect of School
Starting Age on Hyperactivity Scores. 4 to 9 year olds.
Sample
Mean
Young
4.099
3 month
window
N=12491
4.100
6 month
window
N=24878
4.095
16
(2)
(3)
(4)
0.530** 0.477** 0.573*** 0.562***
(0.231) (0.226) (0.199)
(0.199)
2 month
window
N=8293
+ Covariates
(1)
x
(5)
(6)
0.661***
(0.150)
0.714***
(0.149)
x
x
x
x
x
x
x
x
Boys and Girls Compared
17
1
2
3
4
5
6
PMK Assessed Hyperactivity Score - Girls
0
0
1
2
3
Mean Value
4
5
6
PMK Assessed Hyperactivity Score - Boys
-10
0
15-Day Blocks of Age Relative to the Cut-Off Date
10
-10
0
15-Day Blocks of Age Relative to the Cut-Off Date
10
Table 2. Regression Discontinuity Estimates of the Effect of School
Starting Age on Hyperactivity Scores. Boys vs Girls.
Boys
Mean
Young
2 month
window
4.55
3 month
window
4.55
6 month
window
4.62
+ Covariates
N
18
Girls
(1)
(2)
(3)
0.681*
(0.345)
0.935***
(0.295)
0.910***
(0.217)
x
Mean
3.64
x
(4)
(5)
(6)
0.252
(0.25)
0.173
(0.220)
0.523***
(0.178)
x
3.61
x
x
3.57
x
x
x
x
x
x
x
4133
6184
12270
4032
5955
11876
Research Strategy II.
19
Compare children of exactly the same age in
provinces with different cut-offs, so that in one
province, the child is ‘young in class’ while in
the other, he/she is ‘old in class’
 If born in 6 months prior to provincial cut-off

20
Some Provincial Variation in ‘Young’ Variable for DID estimation
Sept 1
Sept 30
Dec 31
Calgary
Quebec, NS
BC, ON, NB, NL
January
February
March
Young
April
Young
Young
May
Young
Young
June
Young
Young
July
Young
Young
Young
August
Young
Young
Young
September
Young
Young
October
Young
November
Young
December
Young
Hyperactivity Scores for April to June
babies with Oct to Dec babies
21
4.8
4.6
4.4
4.2
Quebec
Ontario
4
3.8
3.6
3.4
Young in QC but not ON
Young in ON but not QC
DID Estimation
22
Hyperi      Young6m osip  1  Ageinm onth
si 
 2  Cyclei  3  Gradei    X i   i
All regressions control age in months (have
done everything using higher order terms in
age in months with no change in findings)
Table 4. Difference-in-Difference Estimates of the
Implications of Being “Young in Class” for
Hyperactivity Symptoms.
Boys + Girls
Young
Boy
N
Boys
Girls
(1)
(2)
(3)
0.486***
0.124)
0.515***
(0.157)
0.453***
(0.089)
12270
11876
1.057***
(0.035)
24146
Other covariates included: (Log of) Family Equivalent Income, Parental Education, Family
Structure, Immigrant Status, Child’s Health, Cycle Dummies. Cubic age in months.
23
Robustness Checks
24




Exclude children not in correct grade (very few; no
noticeable change in results)
Include all children (e.g., in private schools – same
results, only very slightly smaller estimated
magnitudes)
Check strategic timing of births? No apparent
pattern
Other reasons for ‘jumps’ at cut-off date? Regress
each covariate on ‘young’ (only mother higher
education marginally significant – positive)
Quebec
BC
.001
.0015
Density
.002
.0025
.003
.0025
.002
.0005
.001
Density
.0015
.0005
-200
-100
0
DisCutOff
100
200
-200
kernel = epanechnikov, bandwidth = 18.9343
0
DisCutOff
100
200
100
200
NS
.003
Kernel density estimate
.002
.0015
.001
.0015
Density
.002
.0025
.0025
.003
Kernel density estimate
.0005
.0005
.001
Density
-100
kernel = epanechnikov, bandwidth = 15.6109
Ontario
-200
-100
0
DisCutOff
kernel = epanechnikov, bandwidth = 14.8736
25
Kernel density estimate
.003
Kernel density estimate
100
200
-200
-100
0
DisCutOff
kernel = epanechnikov, bandwidth = 19.7549
Research Questions about Pre-school
hyperactivity
26
 Does
starting school young still increase
hyperactivity once we control for pre-school
symptoms?
 Do more hyperactive children have a
particularly difficult time being young in
class?
 Are there gender differences?
0
.05
.1
.15
.2
Distribution of Pre-Kindergarten Hyperactivity Score
0
5
10
Hyperactivity Score
Boy
27
Girl
15
28
Control for pre-school hyperactivity in both RD
and DD models
 Use longitudinal sample of children observed
at age 2/3 as well as at ages 4 through 9
 Consider both linear pre-school hyperactivity
scale and ‘high hyperactivity’

Table 5. Controlling for Pre-school Hyperactivity in
Regression Discontinuity Models. 3 month window.
Boys + Girls
Young
(1)
(2)
(3)
0.369*
(0.195)
0.342**
(0.170)
0.343**
(0.170)
0.417***
(0.020)
0.420***
(0.029)
Hyperactivity
Score at 2/3
Hyperactivity at
2/3 X Young
Boy
29
N
-0.005
(0.040)
0.934***
(0.105)
0.784***
(0.100)
9579
0.784***
(0.100)
Table 6. Controlling for Pre-school Hyperactivity in
Difference-in-Difference Estimates.
Boys + Girls
Young
(1)
(2)
(3)
0.430**
(0.141)
0.405**
(0.133)
0.404**
(0.133)
0.410***
(0.005)
0.395***
(0.025)
0.894***
(0.073)
0.894***
(0.072)
Hyperactivity
Score at 2/3
Boy
Hyperactivity at
2/3 X Young
1.030***
(0.075)
0.028
(0.041)
30
Table 6b. Controlling for “High” Pre-school
Hyperactivity in Difference-in-Difference Estimates.
Boys + Girls
Young
(1)
(2)
0.430**
(0.141)
0.293*
(0.148)
1.670***
(0.135)
75th
Hyperactivity above
percentile at age 2/3
Boy
High Hyperactivity at 2/3 X
Young
31
1.030***
(0.075)
0.946***
(0.077)
0.444***
(0.128)
Table 6c. Controlling for Pre-school Hyperactivity in
Difference-in-Difference Estimates. Boys compared to
Girls.
Boys
Girls
Young
0.483**
(0.164)
0.405**
(0.133)
Hyperactivity Score
at 2/3
0.413***
(0.027)
0.375***
(0.026)
Hyperactivity at 2/3
X Young
-0.016
(0.069)
0.076**
(0.024)
9793
9508
N
32
Conclusions
33



Children who are young relative to classmates
exhibit more symptoms of hyperactivity, as assessed
by parents
This is true, even controlling for pre-school
hyperactivity
Children with higher levels of pre-school
hyperactivity (more likely to be boys), have a
particularly difficult time
Policy?
34



Staggered school entry (twice per year?) and/or
extra accommodation for relatively young children?
More recess?
Finland model (formal schooling starts at age 7)
Thanks!
35
Hyperactivity Score by Province
Parent's Report of Child's Hyperactivity
36
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
NL
PEI
NS
NB
QB
Old
ON
Young
MB
SK
AB
BC
Hyperactivity More Persistent for Boys
than for Girls
37
2.5
3
3.5
4
4.5
Age Profile of Parent Report Hyperactivity Score
6
7
8
9
10
Age in Years
Boy
Girl
11
Different Age Patterns for Boys and Girls. RD models. 6
month window.
Boys
Girls
Young
0.910***
(0.217)
0.522***
Days from Cutoff
0.0027**
(0.0010)
0.0006
(0.0008)
38
Different Age Patterns for Boys and Girls. DD models.
Boys
Girls
(1)
(2)
(4)
(5)
Young
0.521***
(0.164)
0.524***
(0.164)
0.433***
(0.089)
0.454***
(0.090)
Age in
Months
0.022
(0.014)
0.033
(0.021)
0.033
(0.013)
0.115***
(0.020)
Age Squared
39
-0.0001
(0.0001)
-0.0007***
(0.0001)