The Washington PostDemocracy Dies in Darkness

Why high schools should let kids sleep in

(AP/Charles Dharapak)

Years of research have suggested that early-morning starts at high schools keep kids from learning and staying healthy. Now there's even stronger evidence that first period will always be a drag on high school students.

In a new study, researchers followed several dozen children ages 9-19 over two and a half years, periodically monitoring their sleeping habits. They gave the subjects an actigraph, a kind of motion sensor worn on the wrist that records whether a person is up and moving about or in bed and likely asleep. They also brought the kids into the laboratory for an evening, swabbing their saliva with cotton every half hour for a few hours before their bedtime to test for a chemical that indicates the body is ready to rest.

Although the risks for young people who don't get enough sleep have been thoroughly studied, the new study is among the more detailed yet published on when adolescents go to sleep, when they ought to go to sleep, when they wake up, and how their sleep habits change over time.

They found that as children get older, their internal biological clocks, or circadian rhythms, shift a couple of hours later in the day. They also become able to stay awake later past when that clock begins to prepare the body for sleep. As adolescents' bodies are changing, they have more and more reasons to stay up, from conversations with friends online to homework to part-time jobs. Whatever the reason, they're awake later and later into the night.

Meanwhile, they're getting up earlier, as middle schools and high schools tend to start early in the day than elementary schools. Once the subjects of the study graduated from high school, they started waking up about two hours later, which the researchers took as an indication that high school had been suppressing the students' natural tendency to sleep in.

The American Academy of Pediatrics issued a detailed statement in August arguing that a typical adolescent should be expected to sleep from about 11 p.m. to about 8 a.m., and calling for secondary schools to start no sooner than 8:30 a.m. Summarizing the research on sleep among the young, the academy noted that where schools have delayed start times, the number of car crashes involving adolescents decreased sharply. Other work points to a small but significant effect on academic performance, and researchers also believe that lack of sleep can lead to obesity and depression in some young people.

Studies of students at schools that have moved their schedules later suggest that students don't take advantage of the change to go to bed later. They continue turning in around the same time and get more sleep as a result.

Rush University's Stephanie Crowley, one of the authors of the new paper, said that many adolescents would benefit from an earlier, set bedtime, but that in their study, there were some kids who just wouldn't have been able to drift off any earlier, whose circadian clocks were running a few hours slow. "The early school start time is especially burdensome for them," she said. "They do have this biological propensity to fall asleep later."

Moving school start times later is a complicated undertaking for administrators. Buses have to be coordinated, football schedules have to be arranged and someone has to look after younger siblings if the older ones are still at school late in the afternoon.

These logistical problems, though, might be easier to deal with than the cultural and biological reasons that young people stay awake too late at night. One study by the Brookings Institution estimated that the benefits of later start times in dollar terms outweighed the costs by a ratio of nine to one.

"It's definitely not an easy task, but I think if people really wanted to do this, it's possible," Crowley said.