Allowing teenagers to start school 25 minutes later improves their sleep patterns and mood, researchers have found.
Researchers surveyed boarding school students aged 14 – 18 about their sleeping habits when they started their school day at 8am, then repeated the questionnaire after switching the start time 8.25am.
They found that, on average, students slept for 29 minutes longer on school nights.
The percentage of students receiving eight or more hours of sleep on a school night also jumped from 18 to 44 percent.
Daytime sleepiness, depressed mood and caffeine use were all significantly reduced after the delay in school start time.
“Sleep deprivation is epidemic among adolescents, with potentially serious impacts on mental and physical health, safety and learning,” said Dr Julie Boergers, of the Bradley Hasbro Children's Research Center in Rhode Island.
“Early high school start times contribute to this problem.
“Most teenagers undergo a biological shift to a later sleep-wake cycle, which can make early school start times particularly challenging.
“In this study, we looked at whether a relatively modest, temporary delay in school start time would change students' sleep patterns, sleepiness, mood and caffeine use.”
The research found that younger students and those sleeping less at the start of the study were most likely to benefit from the schedule change.
And once the earlier start time was reinstituted during the spring term, teens reverted back to their original sleep levels.
The later school start time had no effect on the number of hours students spent doing homework, playing sports or engaging in extracurricular activities.
Boergers, who is also co-director of the Pediatric Sleep Disorders Clinic at Hasbro Children's Hospital, said that these findings have important implications for public policy. "The results of this study add to a growing body of research demonstrating important health benefits of later school start times for adolescents," she said.
"If we more closely align school schedules with adolescents' circadian rhythms and sleep needs, we will have students who are more alert, happier, better prepared to learn, and aren't dependent on caffeine and energy drinks just to stay awake in class."
State schools in Britain start at 9am although many private prep schools begin earlier. Labour has said schools should offer childcare from 8am until 6pm.
Last year the UCL Academy in London became the first in Britain to allow pupils to start at 10am after headteacher Geraldine Davies claimed students were more alert.
The Study was published in the Journal of Developmental & Behavioral Pediatrics.