Sleep experts are warning of an epidemic of sleep deprivation among school-aged children, with some urging educational authorities to alter school hours to allow adolescents to stay in bed longer.

Adequate sleep is the strongest factor in the wellbeing and mental health of teenagers, and a shortage is linked to poor educational results, anxiety and obesity, they say. The French education minister approved a proposal to push back by an hour the start of the school day to 9am for students aged 15-18 in Paris.

It followed the publication in December of a study of teenagers in Seattle which found a “significant improvement in the sleep duration of students” after the start of the school day was delayed by almost an hour.

“The Paris decision can only be a good thing for the children,” said Dr Neil Stanley, author of How To Sleep Well, who has noted increasing sleep problems in children and teenagers. “For the benefit of our children start times should be moved later, bringing them more in line with teenagers’ biological rhythms.”

Mandy Gurney, founder of Millpond Children’s Sleep Clinic, has seen a 30% rise in referrals of school-aged children in the last 12 months. Lisa Artis of the Sleep Council also said there had been a “noticeable rise” in sleep deprivation among school children. “A change in the school day would be beneficial to teenagers, but it would take a massive campaign for it to happen. The school day is designed to fit in with the standard working day.”

School leaders are increasingly raising concerns about overtired children, both in secondary schools and the upper end of primary schools, according to James Bowen, director of NAHT Edge, an offshoot of the head teachers’ union.

But there was not enough “hard evidence” to justify the “drastic step” of changing school hours, he added. “The bottom line is that school leaders are very interested in any approach that may have a positive impact on pupils’ learning, but there are significant logistical barriers to changing the school day” especially for working families, he said.

The Education Endowment Foundation funds Teensleep, a research project by Oxford and Durham universities. Teensleep wanted to evaluate the impact of a later start to the school day, but not enough schools signed up for a trial. Now it is examining the consequences of “sleep education” in schools, with the results due to be published in the spring.

Guidance in providing sleep lessons for pupils aged seven to 16 was rolled out to teachers last month.

Scientists say that humans’ circadian rhythms – the body clock that manages the cycle of sleep and wakefulness – change in adolescence. The cycle shifts two hours in teenagers which means that they are wired to go to sleep and wake up later. “It’s like they’re in a different time zone,” said Dr Michael Farquhar, a consultant in paediatric sleep medicine at the Evelina children’s hospital in London.

“We’re asking them to get up before their body clock is ready, because that’s the way the adult world works. So most teenagers end up sleep-deprived.”

Sleep is the “strongest predictor of wellbeing among teenagers”, said Russell Viner, professor of adolescent health at University College London and president of the Royal College of Paediatrics and Child Health.

He co-authored a paper, published in the British Medical Journal in November, based on a study of more than 120,000 15-year-olds which pointed to increasing evidence of the dangers of inadequate sleep.

“When we think about all the things parents worry about, the effects of sleep are about four times higher than the effects of smartphone use,” he said. “There is major development of the brain in puberty. We need to go back to basics: more focus on sleep, physical activity and diet.”

Farquhar said: “If we could rewire the world to suit teenagers, we’d see benefits. But there are practical difficulties in doing that. So, as a start, schools could not schedule double maths at 8.30am and perhaps make PE the first lesson of the day.”