Computers, cell phones, televisions and video games all keep those who should be asleep wide awake, said Jodi A. Mindell, associate director of the Sleep Center at Children’s Hospital of Philadelphia and coauthor of the study. As a result, more than a quarter of high school students fall asleep in school at least once a week. Fourteen percent don’t make it on time – if at all.

At fault is not just a teenager’s altered circadian rhythm, but the number of distractions keeping them up at night, according to a two-month poll of 1,602 caregivers and their children in grades six through 12.

Nearly all the children surveyed had one gadget in their bedroom, but by 12th grade, 39 percent had more than four electronic items there, the study found.

"Those with four or more electronic devices in their bedroom were twice as likely to fall asleep in school," said Mindell, co-chair of the National Sleep Foundation task force that conducted the poll.

Although late nights might seem like a rite of adolescent passage, Mindell said there are serious consequences, both in school and on the road.

Fourteen percent of the 11-to-17-year-olds said they arrive late or miss school because they oversleep, and 15 percent of those who drive said they drive sleepy at least once a week.

Ira Schwartz, 16, has a cell phone, television, computer and video games in his room – and he shares his bed with three small dogs.

On school days, he falls asleep around 11 p.m., after watching TV or playing a couple of video games, with his alarm set at 6:30 a.m. He’s out the door by 7:15, often skipping breakfast because he’s "too tired," and sometimes catching a quick nap when he gets home at 3 p.m. But it’s better than last year, when he had to be at swim practice at 5 a.m.

"Last year I really was falling asleep in my classes," he said. "And my grades suffered."

An optimal night’s sleep for teens is nine hours, said Mary Carskadon, director of the E.P. Bradley Hospital Sleep center at Brown University and the other study author. But researchers found that almost half slept fewer than eight hours on school nights.

Napping doesn’t help much. Although 18 percent of ninth- to 12th-graders napped four or more days a week, they only sleep about an hour, Mindell said, and that doesn’t make up for the night before.

Professor Bryan Polk, who teaches an 8 a.m. religion class at Penn State Abington, said he has always had a few sleepy students, but things started getting worse about five years ago.

"They leave their cell phones on all night and their friends call them in the middle of the night to say ‘Hey, it’s me, how are you doing?", said Polk, who goes to bed at 10 p.m. so he can get up at 5 a.m. "In my house, if the phone rings in the middle of the night, someone is dead or someone is going to be dead."

Deborah Orel, whose son, Zachary Maron, is in high school, said the late nights are a common discussion among her friends, most of whom are fast asleep when their children are typing away.

Calling late was never a problem when she was a child, she said, because if someone called, the whole house knew about it.

"My friend just told me that she was removing her son’s cell phone because he was on the phone until 12:30 in the morning with his girlfriend," Orel said.

"It’s hard to know if they’re talking on the cell, at least with the laptop, you can see there’s a light." Maron, her son, said he does keep his cell on, but people know not to call after 10 p.m., when he’s wrapping up homework, talking to his girlfriend and instant messaging several friends on the computer.

The researchers said that as children reach puberty, their body clocks tend to readjust to start two hours later, so they are more alert at night and sleepier in the early morning. Mindell and Carskadon said schools should adjust their schedules accordingly, and start later. A few have done so, they said, and found that instead of staying up later, students sleep longer.

But until that happens, some students are thinking that if they can’t sleep longer, they can sleep better. Schwartz, who gave up swimming, took up working at the International House of Pancakes, working the 8 p.m. until 4 a.m. shift. His goal? To buy himself the Tempur-Pedic mattress.

"I laid down on it for a minute at Brookstone and nearly fell asleep," he said.