August 13, 2015 5:51 AM EDT

8:30 a.m.

Start time for middle and high schools recommended by the American Academy of Pediatrics. Research shows adolescents are better off rising later than falling asleep earlier


Number of states in which at least 75% of schools start before 8:30 a.m. The early classes make it more difficult for students to sleep the optimal 8½ to 9½ hours per night


Percentage of students who slept at least eight hours per night in Minnesota high schools that started at 8:30 a.m. or later, according to a 2014 study from the University of Minnesota

This appears in the August 24, 2015 issue of TIME.

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