Backgrounder: Later School Start Times

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  • minutes reflected in the start time change.
  • Sleep onset times did not change, and averaged about 10:40 pm in both 9th and 10th grade.
  • The average amount of sleep on school nights fell from 7 hours 9 minutes to 6 hours 50 minutes, which is significant because the students were already accumulating a sleep deficit.
  • Nearly one-half of the 10th graders showed a reversed sleep pattern on the morning MSLT. This pattern is similar to the sleep disorder narcolepsy, moving immediately into REM sleep before non-REM sleep. The 12 students who showed this pattern did not have narcolepsy, but they did have a mismatch between their school day waking times and their circadian rhythms. Indeed, at 8:30 in the morning, they fell asleep within three minutes.
  • None of the students made an optimal adjustment to the new schedule; none was sleeping even 8 1/4 hours on school nights.

"Even without the pressure of biological changes, if we combine an early school starting time--say 7:30 am, which, with a modest commute, makes 6:15 am a viable rising time--with our knowledge that optimal sleep need is 9 1/4 hours, we are asking that 16-year olds go to bed at 9 pm. Rare is a teenager that will keep such a schedule. School work, sports practices, clubs, volunteer work, and paid employment take precedence. When biological changes are factored in, the ability even to have merely 'adequate' sleep is lost," Carskadon explains.

School Start Time Initiatives and Outcomes



The National Sleep Foundation (NSF) worked with U.S. Representative Zoe Lofgren to introduce legislation that addresses the relationship between school start times and adolescent health, wellbeing and performance. We encourage you to contact your Representatives and urge them to support this bill.


Early results from schools that have changed their start times are encouraging. For example, successful high school start time changes were made in Edina and Minneapolis, Minnesota after the Minnesota Medical Association issued a 1993 resolution, Sleep Deprivation in Adolescents, based on the research that puberty resets teens’ internal biological clocks. The schedule was changed from:

A 7:15 am-1:45