Most of us would probably admit to wanting just a little longer in bed each morning, but some kids in Seattle have official permission – and since the state started experimenting with later school times, it's seen a host of benefits start to appear.

Young people are clocking more hours in bed, attending school more often, and achieving higher grades, according to research that's just been published.

The authors behind the study think that changing school starting times more widely could close the gap between different socioeconomic groups, reduce the chances of pupils feeling tired during the day, and boost their overall health.

"All of the studies of adolescent sleep patterns in the United States are showing that the time at which teens generally fall asleep is biologically determined – but the time at which they wake up is socially determined," says one of the researchers, Gideon Dunster from the University of Washington.

"This has severe consequences for health and well-being, because disrupted circadian rhythms can adversely affect digestion, heart rate, body temperature, immune system function, attention span and mental health."

The shift in school starting times was announced back in 2015, and since then student progress has been monitored in various ways – including the use of sleep-tracking wristbands that are more reliable than self-reported sleep patterns.

All of the district's 18 high schools moved the time of the opening bell ring from 7.50 am to 8.45 am, almost an hour later, though the length of the school day remained the same.

Based on the new study, which looked at 180 children across two of those schools, there was a a median increase of 34 minutes of sleep each night across the students: boosting average sleep on school nights from a median average of 6 hours and 50 minutes to 7 hours and 24 minutes.

On the whole the kids haven't been going to bed later - but they have been sleeping longer, the study shows. The researchers say this fits in with what we know about the biological clocks or circadian rhythms of adolescents, in that they differ from adults.

"To ask a teen to be up and alert at 7.30 am is like asking an adult to be active and alert at 5.30 am," says one of the team, biologist Horacio de la Iglesia from the University of Washington.

That benefit is positive enough, but there were others. Grades were 4.5 percent higher for students after the times were shifted, though only one biology class was tested in this case. Meanwhile, at the school with kids from more economically disadvantaged backgrounds, attendance and punctuality improved as well – though this impact wasn't noticed at the other school.

Why all this experimentation? Kids just aren't getting the sleep they need to stay healthy and alert, with experts recommending 8 hours each night. Research has shown only around a quarter of high school age adolescents are meeting that target.

And we've seen the same measures have a positive impact elsewhere. Research published earlier this year showed that when starting times were pushed back at a school in Singapore, the young people got more sleep and felt more alert.

For teachers in Seattle, there have been tangible benefits. "The difference in the attention and energy level of my students during the morning as compared to the earlier start is night and day," teacher Tracy Landboe, from Roosevelt High School in Seattle, told US News.

We'll have to wait and see whether the steps taken in Seattle are enough to get the practice adopted more widely – having less time in the evenings for homework and social activities is one consequence – but there's a growing amount of evidence that is worth weighing up.

"School start time has serious implications for how students learn and perform in their education," says de la Iglesia. "Adolescents are on one schedule. The question is: What schedule will their schools be on?"

The research has been published in Science.