Teenagers are getting just about four hours of sleep a day because they are so hooked to playing videogames or watching TV.
This is causing one in three students to turn up exhausted at secondary school the next day, a new survey reveals.
The survey was carried out by the Sleep Council, which promotes the importance of a good night's rest to health.
As a result, they spend hours secretly playing games or watching TV or talking on the phone, leaving themselves exhausted and sleep deprived for the next day.
The number of teens not getting enough sleep has experts stunned, for it shows that most do not know how badly lack of sleep can affect them.
"I'm staggered that so few teenagers make the link between getting enough good sleep and how they feel in the day," the Daily Mail quoted Dr Chris Idzikowski, from the Edinburgh Sleep Centre, as saying.
"Teenagers need to wake up to the fact that to feel well, perform well and look well, they need to do something. "This is an incredibly worrying trend. What we are seeing is the emergence of 'junk sleep' - sleep that is of neither the length nor quality to feed the brain with the rest it needs to perform properly at school."
Dr Idzikowski insists that parents are also at fault for kids not getting enough of rest. "Parents these days aren't necessarily as strict as they once were with the lights-out policy," he said. "And with so many distractions, the amount of sleep achieved when at friends has to be highly questionable," he added.
With poor-quality sleep with weight gain and under performance at school, experts recommend that kids get at least eight to nine hours of highquality rest every night.