Patterns of sex and socioeconomic differences in aptitude and achievement were compared among eight countries. A universal pattern appeared in which higher status children scored better than lower status children in aptitude, achievement, and school grades. Peer reputation largely ran the same way, with mild exceptions. The social differences in aptitude are generally less than the differences in achievement, although some countries appear to be approaching effective equality of educational opportunity. No notable systematic sex differences in performance were observed. Where differences appeared, cultural differences seem to be responsible. To the extent that school achievement is itself an important aspect of coping behavior, the socioeconomic bias evident to some degree in all countries constitutes something of a deterrent to the optimal development of working-class youth. However, this prejudice is not so complete a deterrent to equality of learning as it potentially could be. Finally, assumptions about the invariant nature and the comparability of the "same" measures in different cultures need to be critically scrutinized. The "same" measures either are not functionally the same, often, or their results are significantly altered by other influences which may be peculiar to particular societies. (Author/GS)