Table 6.

Characteristics of the children in learning ability group

		Class						Performance
Item			Understand		Do not understand				Good		Poor
			mean	SE	mean	SE	P-valuea		mean	SE	Mean	SE	P-valuea
Age			9.08	0.021	8.71	0.103			9.03	0.022	9.26	0.053
Height			134.7	0.14	132.3	0.72	< 0.001		134.5	0.15	135.1	0.37	0.090
Weight			30.5	0.10	30.5	0.59	0.089		30.2	0.11	31.7	0.29	< 0.001
		N	n	%	N	%	P-valueb	N	n	%	N	%	P-valueb
Gender	Boys	3594	3414	95.0	180	5.0	0.009	3623	2962	81.8	601	16.6	0.001
	Girls	3432	3304	96.3	128	3.7		3438	3022	87.9	476	13.8
School year	1	1389	1305	94.0	84	6.0	0.017	1394	1226	87.9	168	12.1	< 0.001
	2	1273	1213	95.3	60	4.7		1288	1109	86.1	179	13.9
	3	1218	1171	96.1	48	3.9		1223	1052	86.0	171	14.0
	4	1174	1132	96.4	42	3.6		1182	976	82.6	206	17.4
	5	1114	1070	96.1	44	3.9		1113	909	81.7	204	18.3
	6	858	827	96.4	31	3.6		861	712	82.7	149	17.3

^aWilcoxon

^bChi-square test