`ZZZZZ's to A', a campaign to have the school day start later, is being fought in the US. Democratic representative Zoe Lofgren is proposing a bill to give school districts grants of up to $25,000 for schools that start after 9 a.m. The school day in the US can begin as early as 7 a.m. and this is being blamed for sleep deprivation leading to poor concentration from children and teenagers. "Research shows that adolescents need about nine and a quarter hours sleep a night," explains Lofgren.

Telling a teenager to go to bed earlier is not always the answer. Mary Carskadon, professor of psychiatry and human behaviour at Brown University school of medicine, says her research shows that it is biology rather than wilfulness which makes teens stay up late. "Kids are waking up and going to school at a time when their brains are still in night-time mode," she says.