Today's teenagers might be into sleepovers - but they're not into sleep.
Social networking, texting, 24-hour tv and computer games are keeping them up way past even their parents' bedtimes.
And caffeinated drinks don't help.
Meanwhile the evidence is piling up that a good night's sleep is essential for all of us.
While your body's dozing, your brain processes everything you've learned during the day, and all the emotional highs and lows.
Physical functions are regulated, like the hormones that influence how much you want to eat.
So if you're sleep deprived, you're more likely to experience mood swings, free-wheeling appetite, and difficultes in remembering what you learned the day before.
And if you're a teen, you need 9, not 8, hours sleep per night.
These are some of the facts that students at St Paul's High School in Glasgow got to grips with when they took part in a pioneering "sleep class" run by the charity Sleep Scotland.
But can you really teach teens to want to sleep? Clare English joined the class to find out.
By the end of the project, it was clear the theory had sunk in.
But when asked if any of the pupils were now prepared to switch their phones off at night, the answer was a resounding no.
However, they commented that they'd be interested in doing a trial to test the power of sleep for themselves.
An experiment? Clare took them at their word.
She returned to the school for a four day trial - and the results were jaw-dropping.
After just three nights of good sleep, the pupils reported they were more alert, happier, more confident, "nicer"...
and looked better.
Computer games scores were improved, and so was their schoolwork.
The pupils were persuaded.
Sleep is good.
Clare English follows a pioneering attempt to get Scotland's teens to bed on time.