Start school later to prevent sleep-deprived teens: U.S. doctors

"The American Medical Association on Tuesday urged starting school later in the morning for teenagers so they can get enough sleep.

In a new policy adopted on Tuesday, the AMA said middle and high schools should start at 8:30 a.m. at the earliest because research has shown that puberty is accompanied by a biological shift in circadian rhythm that contributes to later bedtimes and wake-up times in adolescents.

The influential doctors group said nearly 10 percent of U.S. high schools today begin at or before 7:30 a.m. as districts try to make time for additional classes, sports and extracurricular activities."