This paper documents how segregation between Black students and White students across U.S. colleges has evolved since the 1960s, explores potential channels through which changes occur, and studies segregation across majors within colleges. The main findings are: (1) Black–White dissimilarity fell sharply in the late 1960s and early 1970s and has fallen more gradually since then. White students' exposure to Black students rose almost continuously from 1968 through 2011 before declining somewhat in recent years. Meanwhile, Black students' exposure to White students increased sharply in the late 1960s and early 1970s and has fluctuated since. (2) There has been regional convergence, although colleges in the South remain more segregated than those in any other region when measured by dissimilarity or by Black students' exposure to White students. (3) A major channel for the decline in segregation is the declining share of Black students attending historically Black colleges and universities. Differences in which U.S. state students attend college play only a small role in creating segregation, and there is moderate evidence that segregation is related to college selectivity stratification by race. (4) Although there is segregation within universities, most segregation across major × university cells occurs across universities.

A number of high schools across the United States have moved to later bell times on the belief that their previous bell times were too early for the “biological clocks” of adolescents. In this article I study whether doing so improves academic performance. I first focus on the Twin Cities metropolitan area, where Minneapolis and several suburban districts have made large policy changes but St. Paul and other suburban districts have maintained early schedules. I use individual-level ACT data on all individuals from public high schools in this region who took the ACT between 1993 and 2002 to estimate the effects of school starting times on ACT scores. I then employ school-level data on schedules and test scores on statewide standardized tests from Kansas and Virginia to estimate the effects of bell times on achievement for a broader sample. The results do not suggest an effect of school starting times on achievement.