About 300 pupils at Hugh Christie Technology College in Tonbridge, Kent, start school at 11.30am and finish at 5.30pm. The theory is that teenagers' brains work better later in the day.
The revised timetable, being followed by pupils from 14 to 18 years old, has had a "powerful impact" since it was introduced in September 2007, according to Jon Barker, the headteacher.
"We were aware of research that said teenagers' brains operate more efficiently at that time of the day and we wanted to investigate," he said. "The feedback from teachers, pupils and parents is very positive."
The experiment at Hugh Christie is set to be replicated this September by students at Monkseaton High School in North Tyneside.
Paul Kelley, the headteacher there, has been running a research project into teenagers' body-rhythms, which suggests that forcing pupils to start earlier in the day has a detrimental impact on their education and health.
Dr Kelley has been administering tests to pupils with Russell Foster, an Oxford academic and chairman of Circadian Neuroscience at Brasenose College. Dr Kelley has asked permission from his governors to introduce an 11am start from September.
Hugh Christie is understood to be the first school in the country to have already introduced wholesale changes to its timetable. The new arrangements are followed by all pupils in Years 12 and 13 and selected pupils in Years 10 and 11 if they are following higher level courses. They start at 11.30am three days a week, have one day with no timetabled lessons and start at 8.30am on a Friday to let them have an early finish for the weekend.
In 2006, the year before the change was introduced, sixth formers were achieving an average of a D grade in each of their A-level entries. Mr Barker expects that to improve to a C grade this year. He does not put all of the improvements down to the timetable, but says it has had a significant impact.
"Our exam results are improving, attendance has improved, teachers report that behaviour is better and parents say that they are no longer having battles with their kids so relationships at home are more relaxed," he said.
"We have been able to offer more choice because a lot of the curriculum is outside of the normal school day. There are fewer clashes and it is easier for students to use specialist accommodation, such as the science laboratories."
The project was launched because the school wanted to experiment with space and time when it was putting together plans for a new building. The new school is only 80 per cent of the size of the old building, but is open for longer.
It has been praised by pupils. Year 12 student Matt Robinson, 17, said: "When you start at 8.30 you spend half of the first lesson of the day waking up. Starting later means you feel awake and can prepare for lessons properly.
"If you like working in the morning, you can do homework then."
IT'S IN THE TIMING
Monkseaton High School in North Tyneside has been working with experts on teenagers' body-rhythms for the past three years. The school has given 200 pupils a series of cognitive tests at different times to replicate larger- scale studies carried out in Germany, Canada and America. It found about a 10 per cent improvement in pupil performance in the afternoon compared to the morning.