Thousands of schoolchildren in France have become guinea pigs in an experiment aimed at synchronising their timetables with their natural body rhythms.
The idea is that children will learn more by actually studying less if they only have lessons when their body clocks are "tuned-in" to academic study.
Two years of research by a team of French chrono-biologists claims to have found a way of harmonising children's biorhythms with the best times for study, sport and relaxation.
The pilot schemes, which begin this month, involve about 5,000 pupils aged 12 to 17 at 16 schools who will find their timetables turned on their heads. Mornings will be crammed with lessons while the afternoons will be virtually free of compulsory activity..
Guy Drut, the French youth and sport minister, who is backing the idea, explained: "What we're trying to do is simply restructure the rhythm of the day to suit the natural rhythms of the children."
In the afternoon children will be free to paint, learn a musical instrument, study local history, play sport or investigate social problems such as public health and drug abuse, M Drut said. "It's about getting more out of fewer hours dedicated to intellectual study, and spending more time on sporting and cultural activities."
At Koechlin primary, a pilot school at Altkirch in the Upper Rhine, the day runs from 8.30am to 11.30am and 1.30pm to 4.30pm, Monday to Friday. Wednesday is traditionally a free day and children attend lessons on Saturday mornings.
But from this month morning lessons will be extended by an hour-and-a-half and classes scrapped on the remaining four weekday afternoons.
"My pupils are delighted," said headteacher Jean-Marc Schreiber. "We want to make the school day less stressful for pupils, and avoid the lunchtime rupture in the daily rhythm which makes Mondays, Tuesdays, Thursdays and Fridays very difficult.
"Several teachers were worried, but most of them have now come around to the idea."
At the beginning of each term pupils receive a list of all the afternoon activities, and the pupil's family pays 10F (70p) for each activity.
The rest of the money for next year's pilot scheme will come mainly from the Ministry for Youth and Sport (Pounds 18 million), with some from local councils and the national family allowance budget.
M Schreiber said: "At this school they can do anything from learning an instrument to skiing, horse-riding, judo, tennis, or learning about fashion.
"None of it is compulsory and we estimate about 5 per cent of children won't take part. If they don't want to that's fine. They can just go off and relax somewhere."