Table 1. Descriptives of and bivariate correlations between the study variables.

	Min.	Max.	M	SD	N	1.	2.	3.	4.	5.	6.	7.	8.	9.	10.
Classroom indices
1.Density	.03	.29	.12	.04	54	‒	‒	‒	‒	‒	‒	‒	‒	‒	‒
2.Proportion of isolates	.00	.50	.06	.09	54	−.47**	‒	‒	‒	‒	‒	‒	‒	‒	‒
3. Segmentation	.33	.98	.69	.17	54	−.74**	.50**	‒	‒	‒	‒	‒	‒	‒	‒
4. Inequality	−.02	.30	.11	.07	54	.62**	−.23	−.67**	‒	‒	‒	‒	‒	‒	‒
5.Classroom size	12	28	21.27	4.69	54	−.20	−.43**	.02	−.09	‒	‒	‒	‒	‒	‒
Achievement and individual indices
6.Academic achievement	2.97	9.37	6.88	0.93	1127	‒	‒	‒	‒	‒	‒	‒	‒	‒	‒
7.Number of helpers	0	14	2.59	2.66	1074	‒	‒	‒	‒	‒	.08**	‒	‒	‒	‒
8.% Isolation	0	1	5.40	‒	1127	‒	‒	‒	‒	‒	−.03	−.24**	‒	‒	‒
9.Centrality	0	.86	.39	.19	1074	‒	‒	‒	‒	‒	.11**	.55**	−.47**	‒	‒
10.% Sex (1 = boy)	0	1	49	‒	1138	‒	‒	‒	‒	‒	−.15**	−.26**	.13**	−.17**	‒

Note.

** p < .01.