The short- and long-run impacts of secondary school absences

•We provide novel evidence on how class-absences in middle and high school affect student short-run learning and long-run education attainment.•We leverage between-subject variation in student absences to account for unobserved student-year specific shocks.•Missing 10 classes in middle and high school reduces math or English Language Arts test scores by 3–4% of a standard deviation and course grades by 17–18% of a standard deviation.•Missing 10 total absences across all subjects in 9th grade reduce both the probability of on-time graduation and ever enrolling in college by 2%.•Learning loss due to school absences can have profound economic and social consequences.