Marsh and Parker (1984) described the big-fish-little-pond effect (BFLPE) whereby equally able students have lower academic self-concepts in high-ability schools than in low-ability schools. The present investigation, a reanalysis of the Youth in Transition data, supported the generality of the earlier findings and demonstrated new theoretical implications of the BFLPE. First, differences in the academic self-concepts of black and white students, sometimes assumed to represent response biases, were explicable in terms of the BFLPE. SEcond, equally able students earned higher grades in lower-ability schools. This frame-of-reference effect for grades was distinct from, but contributed to, the BFLPE for academic self-concept. Third, a longitudinal analysis demonstrated that academic self-concept had a direct effect on subsequent school performance beyond the effects of academic ability and prior school performance. About one-quarter of this effect could be explained in terms of the BFLPE. Six pages of references, tabulated data, and the models showing the cause-effect relationship of various factors follow the report. (Author/JAZ)