"At puberty the architecture of sleep changes," says Maas. Until adolescence, melatonin, the hormone that triggers the onset of sleep, is released in the afternoon as daylight fades. But for reasons that are still unclear, teens receive these hormonal signals later in the evening, delaying the time they start to feel sleepy by about two hours.
Sleep Solution: Reset the internal clock.
A consistent bedtime routine is just as important now as it was when he was a toddler. To prove it to him, pick one week when he'll test out your theory. First, work backward by subtracting 10 hours from when he needs to wake up. If your 13-year-old's alarm rings at 7 on school days, then the TV needs to go off at 9 each night followed by a half-hour of (nonscreen) mellow activities like reading for pleasure. For the 16-year-old who you let sleep till 9:30 on the weekends, set her curfew for 11:30 so she's asleep by midnight. Another option is to have your child go to sleep 15 minutes earlier every night for four or five nights until he regains an hour. "If he thinks your edict will be in force all year, he won't agree," says Mindell. "But for one week? He can do that. And he'll be surprised at how dramatically different he feels."