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Descriptive analyses of the participants across the four time points
| Time point | Academic year | Number of participants | Mean age (SD) |
|---|---|---|---|
| Time 1 | 2009/10 | 3328 | 12.59 (.743) |
| Time 2 | 2010/11 | 2905 | 13.59 (.697) |
| Time 3 | 2011/12 | 2668 | 14.54 (.680) |
| Time 4 | 2012/13 | 2427 | 15.49 (.656) |
