The school bells ring at 7:30 am, but evidence is mounting that starting school this early adversely impacts our children’s academic performance, long term health and lifetime career earnings—because they are sleep deprived. To reverse this development, policy makers should consider pushing back school start times, by at least an hour.

Primary school children need between nine and 10 hours of sleep, whereas teenagers require between eight and nine. But because many children, particularly teenagers, tend to go to bed late, early waking times deprive them of much-needed sleep.

Contrary to popular belief, and despite overwhelming anecdotal evidence, children and teenagers do not modify their sleep habits to spite their parents. We have long known that our circadian rhythm, the body’s internal 24-hour clock, changes with age.

As children hit puberty, their natural sleep cycles gradually become delayed, turning teenagers into night owls. This trend continues until the end of adolescence, before reversing itself over time.

This physiological change is compounded by the amount of time spent on digital devices, which kids are exposed to much earlier these days. Highly addictive content on platforms like Netflix and YouTube, coupled with the need to cultivate the perfect online presence on social media sites like Facebook and Instagram, all combine to take precious hours away from sleep.

The secretion of melatonin—a hormone that regulates sleep and wakefulness—is suppressed by blue light emanating from these screens, further disrupting the body’s ability to fall asleep naturally by tricking our brains into thinking it’s still daytime.

According to a 2016 survey, Malaysians spend about 14 hours per day on digital gadgets. If we subtract the eight hours adults spend at work looking at computers, children are probably spending six hours on some form of screen, which corresponds with data from the U.S. and U.K.

From reduced attention spans and impaired memory to mood swings and slower reaction time, sleep deprivation puts children at risk of various health issues. Sleep deprivation also increases the risk for type 2 diabetes, cancer and mental illness, among others.

In the United States, health and civil society organisations are lobbying for schools to start no earlier than 8:30am, and some states have already enacted laws related to school start times.

Skeptics of starting school later believe that keeping “adult” hours builds character and prepare teenagers for the “real” working world.

Another reservation to later start times is usually expressed by parents, who worry about childcare and transportation. Communities also peg its social cadence around school hours and so bus companies and enrichment centres built around prevailing school hours have an interest in maintaining the status quo. However, these reasons pale in comparison to the damage we’re doing by continuing to deprive children of the sleep they need.

The good news is that starting school later is very doable in Malaysia, and we have already done it to cope with increased student enrolments by assigning classes in younger age groups to afternoon sessions.

While there is limited evidence showing that students in afternoon classes attain better grades, studies on American kids in schools which start later show that they get more sleep, miss fewer classes and—for the newly licensed—get into fewer road accidents.

To not consider starting school later is to disregard science.

Listen to the podcast 'Adolescents & Sleep':