By Anthony Baxter
Some people think teenagers would do better if school began at 11am
Getting by on just a few hours, then catching up at the weekend - it's a tried and tested sleep habit for lots of people.
It's also something that doctors say isn't great for people's health and, for teenagers, could actually be quite damaging.
More and more young people aren't getting enough shut eye, and it's making them fat, grumpy and even unpopular.
That's according to top sleep expert Doctor Neil Stanley.
He's been talking to the BBC Two show Revealed as part of their investigation into how important sleep is for teenagers.
Kalan, 15, says sleep is something that gets in the way of more important things.
"Last week I went to bed about 3am and got up at 8am," he said.
"I'm probably texting, or I'll be on my phone. [I feel] like I'll be missing out on MSN and television programmes [if I went to bed early]."
Kalan gets around four to five hours sleep a night, and says that any more than that makes him feel rough.
"I've got my eight, nine hours sleep [before], and I've just become more tired and grouchy."
Doctors say texting, gaming, the internet and online messaging are some of the main reasons why more young people are staying up late.
They say people can get by on as little as four hours sleep, but for most people it can lead to serious problems.
Scientists have made links made between sleep deprivation and obesity and mental health problems.
Doctor Neil Stanley from Norfolk and Norwich University Hospital has been studying sleep for years.
"People see sleep as a time of doing nothing," he explained, "and yet your body is repairing, your mind is dealing with the emotion of the day, you're learning new things. All of these things happen, it's important stuff."
He says trying to catch up on missed hours at the weekend doesn't work.
"It's like eating burgers all week, then eating lettuces at the weekend, and saying you eat healthily. Your body really wants a good night's sleep every night."
Research shows that teenagers' body clocks are different from adults and children, and that wanting to stay up late and then not being able to get up in the morning isn't just laziness.
It's something that's controlled by hormones and a chemical called melatonin.
Britnay reckons a late start would make people to go to bed later
The teenage sleep cycle is something that Doctor Paul Kelley, the head teacher of Monkseaton School in Whitley Bay, takes very seriously.
"Young people and adults have been at loggerheads about sleep for hundreds of years," he said, "and now that we understand the chemical and biological drive, then adults actually have to adjust to young people, and that's about time."
Students at the school took part in memory tests, and the results showed they had better concentration later in the day.
As a result Doctor Kelley has now asked his school governors to consider moving the start time for lessons to 11am so that his students get a lie-in.
"The real issue is sleep deprivation. Young people aren't having the chance to sleep as long as they could because they have to get up earlier than their body tells them to."
Tayler is one of the students who took part in the tests.
"I could sleep 'til 10am quite easily," he said, "but with my mum it's not an option."
He says the 11am start would be a good thing, not just because of the lie-in, but also because it might help with school work.
However, Britnay, who also took part in the tests, had a different view.
"If I get up later, it'll encourage me to stay up later," she said. "The school routine is getting up early, and finishing at 3pm."
Sleep's not sexy
Doctor Neil Stanley says sleep is just as important as diet and exercise, but it's not being promoted.
"Nobody is making sleep desirable or sexy," he explained. "It's not like David Beckham says, 'I play better football because I've had a good night's sleep', there's nobody selling that idea."
Kalan only sleeps four or five hours a night
Although scientists still don't know exactly why it is we need to sleep, it's now known that the "eight hours a night rule" doesn't work for everyone.
The number of hours we need varies from between four and 10 hours a night.
Most people spend around a third of their lives in bed but 15-year-old Kalan says not needing as much sleep means he has more time to do the things he enjoys.
"Because I'm young, I live for the weekend, so being in at the weekend sleeping is just rubbish," he said. "When I get older I might change my ways and sleep a lot more."