Teenagers are notoriously bad at getting out of bed in the morning, but new research suggests that delaying school start times would still not help them to get the rest they need.
The research contrasts with findings suggesting that school should start later to align more closely with teenagers' “body clock”.
The academics from Surrey University and Harvard Medical School who carried out the latest research argue that delaying school start times would simply cause most teenagers' internal clocks to drift later, and in a matter of weeks they would find it just as hard to get out of bed.
The problem, they say, is teenagers' exposure to light. Getting up late in the morning leads to them leaving the lights on later at night, which delays their biological clock - in turn making it harder to get up.
A better solution, they argue, would be increasing exposure to bright light during the day, turning lights down in the evening and off at night.
Turning down the lights, the researchers stress, also means switching off devices such as tablets and smartphones.
The research, published in Scientific Reports, used mathematical modelling to predict the impact of delaying school start times.
The analysis took into account factors such as whether someone is naturally a morning or evening person, the effects of natural and artificial light on body clocks and the typical time of an alarm clock.
Lead author Dr Anne Skeldon said: "What comes out of the maths is that teenagers are more sensitive to light, so there are physiological differences for teenagers.
"But if you were to look at teens who were hunter gatherers they wouldn't have had a problem getting up in the morning. Modern lifestyles make it harder for people to get up."
Instead of moving UK school times, the modelling suggests that young people should be exposed to bright light during the day, with lights - including from phones and devices - turned down in the evening and off at night.
"There's been quite a lot about devices, and that's all consistent with what comes out of the modelling - light in the evening delays sleep," Dr Skeldon said.
She added that mathematics allows researchers to use existing knowledge about how light interacts with the biological clock to make predictions about what can help someone to get more sleep.
She said: "It highlights that adolescents are not 'programmed' to wake up late and that by increasing exposure to bright light during the day, turning lights down in the evening and off at night should enable most to get up in time for work or school without too much effort and without changing school timetables."