It is a truism of research on social stratification that the effects of socioeconomic or family background on educational attainment lead to biases in the simple regression of occupational status (or other putative outcomes of schooling) on educational attainment. Using a structural equation model of sibling resemblance in educational attainment and occupational status, Hauser and Mossel have found minimal evidence of family bias in the effects of postsecondary schooling on occupational status in a sample of Wisconsin brothers. In order to resolve this seemingly anomalous finding, the present analysis compares the Hauser-Mossel findings with those in larger samples of sibling pairs of the same and of mixed sex in the Wisconsin Longitudinal Study and with pairs of brothers in Olneck's Kalamazoo study. In the course of the analysis, some methodological problems in cross-population comparisons of structural equation models are solved. The comparative analysis shows that family bias in the effects of schooling on occupational status may be much less than is commonly believed and that very large samples may be needed to measure it reliably. Moreover, the analysis suggests that estimates of family bias are very sensitive to the specification of response variability in schooling. (Author)