Wave 1
|
Cohort
|
Total
|
X1
|
X2
|
X3
|
X4
|
X5
|
X6
|
X7
|
X8
|
X9
|
X10
|
N
|
504
|
15
|
30
|
62
|
47
|
13
|
34
|
119
|
104
|
54
|
26
|
Mean Age (SD)
|
13.4 (.7)
|
12.6 (.4)
|
11.7 (.3)
|
13.4 (.3)
|
13.4 (.3)
|
12.2 (.4)
|
12.8 (.3)
|
14.0 (.4)
|
13.1 (.3)
|
14.3 (.3)
|
13.2 (.3)
|
Year group
|
7–9
|
7–8
|
7
|
8
|
8
|
7–8
|
8
|
9
|
8
|
9
|
8
|
Gender (% Female)
|
55%
|
40%
|
50%
|
100%
|
100%
|
100%
|
47%
|
0%
|
100%
|
0%
|
58%
|
Ethnicity (% Caucasian)
|
75%
|
60%
|
87%
|
68%
|
72%
|
69%
|
59%
|
86%
|
69%
|
76%
|
85%
|
SES (Median, IQR)
|
4 (2)
|
4 (2)
|
3 (2)
|
4 (2)
|
3 (2)
|
4 (2)
|
2 (2)
|
4 (1)
|
4 (2)
|
4 (2)
|
3 (2)
|
Wave 2
|
Cohort
|
Total
|
X1
|
X2
|
X3
|
X4
|
X5
|
X6
|
X7
|
X8
|
X9
|
X10
|
N
|
450
|
9
|
25
|
60
|
40
|
6
|
26
|
109
|
101
|
50
|
24
|
Mean Age (SD)
|
14.5 (.6)
|
14.0 (.4)
|
13.3 (.3)
|
14.5 (.3)
|
14.8 (.3)
|
13.5 (.2)
|
14.0 (.3)
|
15.1 (.4)
|
14.1 (.3)
|
15.4 (.3)
|
14.3 (.3)
|
Year group
|
8–10
|
8–9
|
9
|
9
|
10
|
8–9
|
9
|
10
|
9
|
10
|
9
|
Gender (% Female)
|
56%
|
56%
|
52%
|
100%
|
100%
|
100%
|
42%
|
0%
|
100%
|
0%
|
58%
|
Ethnicity (% Caucasian)
|
75%
|
56%
|
84%
|
67%
|
73%
|
67%
|
65%
|
86%
|
69%
|
74%
|
42%
|
SES (Median, IQR)
|
4 (2)
|
4 (2)
|
3 (2)
|
4 (2)
|
3 (2)
|
4 (2)
|
2 (2)
|
4 (1)
|
4 (2)
|
4 (2)
|
3 (2)
|
Wave 3
|
Cohort
|
Total
|
X1
|
X2
|
X3
|
X4
|
X5
|
X6
|
X7
|
X8
|
X9
|
X10
|
N
|
411
|
8
|
22
|
62
|
37
|
12
|
12
|
92
|
92
|
50
|
24
|
Mean Age (SD)
|
15.7 (.6)
|
15.3 (.4)
|
14.8 (.3)
|
15.9 (.3)
|
15.8 (.3)
|
14.5 (.4)
|
15.0 (.3)
|
16.0 (.4)
|
15.4 (.3)
|
16.1 (.3)
|
15.3 (.3)
|
Year group
|
9–11
|
10–11
|
10
|
11
|
11
|
9–10
|
11
|
11
|
11
|
11
|
10
|
Gender (% Female)
|
58%
|
50%
|
46%
|
100%
|
100%
|
100%
|
67%
|
0%
|
100%
|
0%
|
58%
|
Ethnicity (% Caucasian)
|
76%
|
63%
|
86%
|
68%
|
73%
|
75%
|
75%
|
85%
|
70%
|
74%
|
88%
|
SES (Median, IQR)
|
4 (2)
|
4 (2)
|
3 (2)
|
4 (2)
|
3(2)
|
4 (2)
|
2 (2)
|
4 (1)
|
4 (2)
|
4 (2)
|
3 (2)
|
- Note: Update from the protocol paper (Booth et al., 2017); age has now been coded to two decimal places, and SES (Socio-Economic Status) is the median of both mother and father education level; SD Standard Deviation; IQR Interquartile Range; 11% attrition at Wave 2 and 19% attrition by Wave 3