Blacks and Mexican Americans do not attain the levels of education enjoyed by whites. There are two possible explanations for these differences: (1) either the process of educational attainment varies across ethnic groups, or (2) if the process is invariant, whites start with social advantages not shared by blacks and Mexican Americans, and thus demonstrate higher educational outcomes. Using data from the 1972 National Longitudinal Study (NLS), and controlling for known differences in measurement errors across groups, statistically significant interactions in the attainment of blacks, Mexican Americans, and whites were found. These differences in structural parameters, however, were not large enough to account for the different educational outcomes across ethnic groups. Differences in outcome appear to be primarily a function of differential levels of social background. Thus, equality of educational opportunity will not equalize outcome when groups are not equal to begin with. (Author/APM)