You are grumpy, unpopular and hungry all the time - could that be down to a lack of sleep? Too little can affect mood and intelligence, but does everyone really need eight hours?

18-year-old Stephanie loves her sleep and gets as much as possible, while 15-year-old Kalan stays up late and gets up early. What will happen when they swap sleep habits? And will their mates notice a difference?

Reporters Anthony Baxter and Tina Daheley ask how important sleep really is and meet the head teacher who thinks school should start at 11am to allow pupils a lie-in. Show less