In contrast to past studies of Black-White differences, most of which have been cross-sectional in design, this study compared longitudinally the academic growth of Black and White students who attended the same high schools and were enrolled in the same curricula. As participants in a nationwide study of academic growth the students had taken a battery of ability and achievement tests in grades 5,7,9, and 11. At grade 5 the Black students were one to two years behind the White students and on most tests--but not all--the gap increased over time. Analyses of covariance indicated, however, that usually the gap was no more than would be predicted on the basis of the initial differences in mean scores between the groups. The groups also differed appreciably in socioeconomic status.