Table 1.

Sample characteristics

	Study 1		Study 2
	n	% Boys	n	% Boys
Grade 1	862	51.6	20	65.0
Grade 2	840	53.9	34	47.1
Grade 3	847	51.2	33	57.6
Grade 4	854	48.6	16	68.8
Grade 5	850	49.9	16	56.3
Grade 6	914	49.8	21	42.9
Total	5,167	50.8	140	55.0