A new study shows that after a one-hour delay of school start times, teens increased their average nightly hours of sleep and decreased their "catch-up sleep" on the weekends, and they were involved in fewer auto accidents.

When school started one hour later students averaged from 12 minutes (grade nine) to 30 minutes (grade 12) more self-reported nightly sleep. The percentage of students who got at least eight hours of sleep per weeknight increased significantly from 35.7 percent to 50 percent; students who got at least nine hours of sleep also increased from 6.3 percent to 10.8 percent. The average amount of additional weekend sleep, or "catch-up sleep," decreased from 1.9 hours to 1.1 hours. Daytime sleepiness decreased, as reported by students using the Epworth Sleepiness Scale. Average crash rates for teen drivers in the study county in the two years after the change in school start time dropped 16.5 percent compared to the two years prior to the change, while teen crash rates for the rest of the state increased 7.8 percent over the same time period.

A survey concerning the sleep habits of students from an entire county-wide school district in Kansas was distributed before and after a change in school start times.

Source: Science Daily
http://www.sciencedaily.com/releases/2008/12/081215074351.htm