Waking up at the crack of dawn for another day of school isn’t fun for anyone: not for the millions of kids who have to be at school before 8:30 AM and certainly not for the parents who have to drag those kids out of bed. And once again, sleep scientists say schools should stop trying to fight teenagers’ circadian rhythms and wait until 10 AM to start.

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The fact that more sleep makes teens (and adults) healthier and better at learning isn’t really new. But recently a group of British sleep scientists argued that school shouldn’t start until at least 10 AM for kids to get the most out of their day.

"At the age of 10 you get up and go to school and it fits in with our nine-to-five lifestyle," Kelley said recently at the British Science Festival, David Barnett reports for The Guardian. "When you are about 55 you also settle into the same pattern. But in between it changes a huge amount and, depending on your age, you really need to be starting around three hours later, which is entirely natural."

The problem, Kelley says, is that not many people between the age of 10 and 55 are really suited to waking up at the break of dawn, especially not high schoolers and college students. Even most adults’ circadian rhythms are not suited to rising early, although Kelley says adolescents are most affected by struggling to get up early, Jonathan Webb writes for the BBC.

"Most people wake up to alarms, because they don't naturally wake up at the time when they have to get up and go to work,” Kelley tells Webb. "So we've got a sleep deprived society - it's just that this age group, say 14-24 in particular, is more deprived than any other sector.”

Even the Centers for Disease Control seem to have gotten the message. For the first time, the CDC is urging school districts and policymakers to push back start times after a study of public schools across the country found that more than 75 percent started before 8:30 AM in more than 40 states.

“Getting enough sleep is important for students’ health, safety, and academic performance,” said Anne Wheaton, the study’s lead author and epidemiologist in the CDC’s Division of Population Health said in a statement. “Early school start times, however, are preventing many adolescents from getting the sleep they need.”

While the CDC may now be urging later start times, they don’t go quite as far as Kelley’s 10 AM proposal – in a statement, the CDC reports that an 8:30 AM start time would allow teenagers to get the recommended 8.5 to 9.5 hours of sleep a night, so long as they went to bed around 11 PM or 12 AM.