Teenagers slept 38 minutes longer when schools started an hour later, trial finds

Teenagers at schools that pushed their start time back by an hour slept an average of 38 minutes longer each night and were significantly less likely to be absent, according to the largest controlled trial of later school starts yet conducted in Britain.

The study, led by researchers at a sleep research institute in Manchester and published this week, followed 6,800 pupils aged 13 to 16 at 12 secondary schools across Greater Manchester over two academic years. Six schools moved their first lesson from 8.30am to 9.30am for a full year; six matched schools kept their existing timetables. Pupils wore wrist monitors for two weeks each term and completed sleep and mood questionnaires.

The results were clearer than the researchers had anticipated. Pupils at the late-start schools gained an average of 38 minutes’ sleep a night, mostly because they did not, as sceptics had predicted, simply stay up later: bedtimes shifted by only nine minutes on average. Unauthorised absence fell by 16% relative to the control schools, and scores on a standard adolescent wellbeing scale improved modestly. Teachers reported fewer behaviour incidents before 11am.

“The biology here is not controversial,” said Prof Rachel Dunmore, who led the trial. “Adolescent circadian rhythms shift later by about two hours during puberty. Asking a 15-year-old to be in a classroom at 8.30am is roughly equivalent to asking an adult to be at work at 6.30am. What this study shows is that when you change the timetable, the sleep actually follows. That was the open question.”

The trial also documented the costs. Parents at the late-start schools were more likely to report difficulties with childcare for younger siblings and with their own working hours, and two of the six schools had to renegotiate bus contracts at additional expense. Pupils with part-time jobs or caring responsibilities found the later finish, at 4.30pm, harder. The researchers said these problems were “real and unevenly distributed” and that any wider adoption would need to address them directly.

One of the participating heads, Marcus Ellery of a 1,200-pupil academy in Rochdale, said the school had decided to keep the later start permanently. “The first two months were hard. Parents were cross. Then the attendance figures came in and the cross parents went quiet,” he said. “What I didn’t expect was the staff. Several of them told me they’d been fighting a losing battle with period one for 20 years and had assumed it was the kids. It wasn’t the kids.”

The Department for Education said it would “consider the findings carefully” but that start times were a matter for individual schools. Dunmore said she hoped the study would “move the conversation from whether to how”.