After a long day, you’re finally ready to hit the sack, but your teen is still on the computer and it’s almost midnight.

“Child insomnia is a big problem in kids these days,” says child psychologist Dr. Penny Corkum. “Our whole sleep cycle is based on light. With kids, especially older kids, they’re on MSN and they’re being bombarded by lights into the night. It messes with their melatonin, which is the hormone that helps you regulate your sleep,” she says. With homework and extra-curricular activities such as part-time jobs, many teens are pushing the envelope. So what can you do? In addition to encouraging a regular bedtime, limit caffeine and have a no TV, cell phone or computer rule for late at night. Make sure he’s getting enough physical activity during the day and if he works, ensure his shift ends early in the evening.

Researchers at McMaster University in Hamilton, Ont., found that more than half of the 2,201 high school students surveyed got less than 8.5 hours of sleep on a typical weeknight.

Keep reading for more sleep tips for teens