RT Journal Article SR Electronic T1 Rise and Shine JF Journal of Human Resources JO J Hum Resour FD University of Wisconsin Press SP 957 OP 992 DO 10.3368/jhr.53.4.0815-7346R1 VO 53 IS 4 A1 Heissel, Jennifer A. A1 Norris, Samuel YR 2018 UL http://jhr.uwpress.org/content/53/4/957.abstract AB We analyze the effect of school start time on academic performance. Sleep patterns are determined in part by sunrise times, which vary across time zones. Because school start times do not fully reflect this difference, we instrument for the hours of sunlight before school with the time zone boundary in Florida. We find that moving start times one hour later relative to sunrise increases test scores by 0.08 and 0.06 standard deviations for adolescents in math and reading, respectively. In math, the effect is larger for older children and co-varies with entry into an important pubertal stage. School districts can improve performance while maintaining the current distribution of start times by moving classes earlier for younger children and later for older children.