my house I can't even begin to tell you," added Owens, whose daughter just graduated from the school and who participated in the experiment. "Many of the faculty members said the same thing: that it improved the quality of their lives as well as the perception that students were just better rested and more ready to start the day."

The study bolsters the evidence that teens have special sleep needs.

"Sleep medicine specialists have long known that delaying high school start times helps teenagers sleep better," said Dr. Heidi V. Connolly, chief of the division of pediatric sleep medicine at the University of Rochester Medical Center in New York. "Teenagers are biologically programmed to prefer a later bedtime and a later wake-up time so it is not surprising that theystruggle with early school start times."

Adolescents' circadian rhythms do shift during puberty. "What that boils down to is that teenagers are not able to fall asleep as early as they did when they were in middle school or elementary school," Owens explained. "There is as much as a two-hour shift in sleep-wake cycles."

But while they may be going to bed later, they still need the same amount of sleep, making sleep deprivation "rampant among American teens," Connolly said.

Owens was approached by St. George's School in Middletown, R.I., about doing a study on a later school start time.

"There was a lot of push back initially from faculty, administration and athletic coaches who felt that half an hour wasn't going to make a substantial difference and was going to be