The authors analyze nationally representative data from 1972, 1982, 1992, and 2004, examining the mathematics achievement of four high school senior cohorts, and several school and family background characteristics. The authors examine how changes in these measures relate to the black-white and Latino-white test score gaps and to changes in school minority composition. Understanding how our society can address these countervailing forces—the improving socioeconomic conditions for black and Latino families on the one hand, and the increasing racial isolation of these students in schools on the other—necessitates innovative ideas and experimentation.