Sleepmore in Seattle: Later school start times are associated with more sleep and better performance in high school students

This natural experiment provided compelling evidence that chronotype-aware scheduling improves outcomes. When Seattle Public Schools delayed start times from 7:50 AM to 8:45 AM, students slept 34 minutes more, grades improved 4.5%, and absences decreased 15%.

Critically, benefits were concentrated in owl chronotypes who had been most disadvantaged by early start times. Larks, already getting sufficient sleep, showed little change. This demonstrates that schedule optimization should consider individual circadian variation.