Table 1.

Number of collected questionnaires across waves.

N (School)	Wave 1	Wave 2	Wave 3	Wave 4	Wave 5	Wave 6	Wave 7	Wave 8
	48	47a	44b	44c	43	43	43	43
No. of participants	7,846	7,388	6,939	6,697	6,876	6,733	6548	6492
Control Group	3,797	3,654	3,765	3,698	3,757	3,727	3669	3640
Male	1,936	1,876	1,896	1,888	1,874	1,894	1,894	1,865
Female	1,613	1,619	1,666	1,599	1,682	1,679	1,689	1,716
Experimental Group	4,049	3,734	3,174	2,999	3,119	3,006	2,879	2,852
Male	2,154	1,998	1,691	1,548	1,632	1,591	1,536	1,533
Female	1,745	1,571	1,283	1,259	1,312	1,278	1,225	1,272
% of successfully matched	98%	96%	97%	98%	99%	97%	93%	91%

^a1 Experimental school (n = 207) had withdrawn after Wave 1.

^b3 Experimental schools (n = 629) had withdrawn after Wave 2.

^c1 Experimental school (n = 71) had withdrawn after Wave 4.