Appendix 2
Proportion of Variance at
the School Level
Within the framework of the variance components models reported in this volume, one
way of assessing the extent of school differences is to consider the proportion of the total
(unexplained) variance that is attributable to the school level. In the case of models having
only the grand mean in the random part (in which, therefore, the slopes do not vary between
schools) a single statistic can be quoted, which gives the proportion of the variance
attributable to the school level. In the case of models having one or more of the independent
variables in the random part (in which some of the slopes therefore vary between schools)
a single statistic cannot be quoted. In such models, the proportion of the variance
attributable to the school level depends on the characteristics of the pupil (on the values
taken by the variables included in the random part).
The tables below show the proportion of the variance attributable to the school level
for the more important models having one or more independent variables in the random
part. (For the simpler models having only the grand mean in the random part, the single
figure has been quoted in the text.)
Table A1
Proportion of variance of the school level: outcome -- second-year reading score
Percentages
Country of origin
Socio-economic group
Neither parent has worked
Unskilled manual
Semi-skilled manual
Skilled manual
White collar
Professional or managerial
UK
14.1
10.0
8.9
9.4
12.3
16.9
South Asian
10.0
6.0
4.2
4.8
7.6
13.0
Other
14.6
11.1
9.5
10.0
12.9
17.4
319
The School Effect
Table A2
Proportion of variance at the school level: outcome -- second-year maths score
Percentages
First-year maths score
5
10
15
20
25
Table A3
9.0
7.0
6.4
7.3
9.6
Proportion of variance at the school level: outcome -- total exam score
Percentages
Country of origin
Second-year reading score
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
320
UK
8.5
6.6
4.9
3.5
2.5
1.8
1.5
1.6
2.0
2.9
4.0
5.5
7.3
9.4
11.7
South Asian
12.3
10.5
8.9
7.7
6.8
6.2
5.9
5.9
6.4
7.1
8.2
9.6
11.2
13.1
15.2
Other
8.4
6.5
4.8
3.4
2.4
1.7
1.4
1.5
1.9
2.7
3.9
5.4
7.2
9.3
11.6
Appendix 2
Table A4
Proportion of variance at the school level: outcome -- English exam score
Percentages
Country of origin
Second-year score
UK
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
9.9
7.3
5.6
4.1
3.0
2.2
1.7
1.6
1.5
2.4
3.2
4.5
5.6
7.7
9.7
Table A5
South Asian
17.8
15.4
13.9
12.6
11.6
10.9
10.5
10.3
10.5
11.0
11.8
12.9
14.2
15.8
17.6
Other
15.8
13.5
12.0
10.7
9.8
9.0
8.6
8.5
8.6
9.2
10.0
11.0
12.3
13.8
15.6
Proportion of variance at the school level: outcome -- maths exam score
Percentages
Second-year maths score
10
15
20
25
30
35
40
45
50
18.1
11.8
6.8
3.6
2.6
3.9
7.5
12.7
19.1
321