Teenage sleeping patterns

An interesting article at the New York Times:

It's Monday morning, and you’re having trouble waking your teenagers. You're not alone. Indeed, each morning, few of the country's 17 million high school students are awake enough to get much out of their first class, particularly if it starts before 8 a.m. Sure, many of them stayed up too late the night before, but not because they wanted to.

Research shows that teenagers' body clocks are set to a schedule that is different from that of younger children or adults. This prevents adolescents from dropping off until around 11 p.m., when they produce the sleep-inducing hormone melatonin, and waking up much before 8 a.m. when their bodies stop producing melatonin. The result is that the first class of the morning is often a waste, with as many as 28 percent of students falling asleep, according to a National Sleep Foundation poll. Some are so sleepy they don’t even show up, contributing to failure and dropout rates.