A new, national survey released by the University of Michigan has found that 50 percent of parents who have teenage children would support later start times for high school. That number might not impress you. But it is much higher than even a few years ago, when many parents felt that such a change would cause practical problems. A steady drumbeat of studies showing that teens who start school later are healthier, safer and smarter is having a real affect on public opinion. As a result, more and more school districts across the U.S. are beginning the day later or are considering doing so.

The university conducted the survey of 636 parents of teens in November and December 2014 after the American Academy of Pediatrics released a policy statement saying that middle and high schools should begin class at 8:30 a.m. or later. The recommendation brought a lot of attention to the issue, which has simmered for years. Although the Michigan study found that only 20 percent of parents had heard about the academy’s recommendation, when the pollsters told parents about it, 71 percent agreed with the endorsement.

The growing awareness is opportune because a different study released Monday by the Columbia University School of Public Health reported that American teens have become increasingly sleep deprived over the past 20 years. In 1991, for example, 72 percent of 15-year-olds reported getting seven or more hours of sleep regularly; in 2012 only 63 percent of that age group slept that much. The National Sleep Foundation recommends that teens get nine hours a night—more than adults or younger children.

Studies demonstrating the benefits of later high school start times are piling up. That’s because biological research confirms that circadian rhythms shift during the teen years, pushing boys and girls to stay up later at night and sleep later into the morning. Forcing them to start school early—before 8:00 a.m. in many districts around the country, cuts into their natural sleep cycles. That, in turn, makes them groggy during early morning classes and can undermine their attention the entire day.

A large examination last year by Kyla Wahlstrom at the University of Minnesota that tracked more than 9,000 students in eight public high schools found that grades earned in math, English, science and social studies typically rose after just one semester of delaying the opening bell to 8:35 a.m. or later. A 2012 survey of North Carolina school districts found that later start times correlated with higher scores in math and reading. Other recent investigations link later starts to higher school attendance and lower depression rates among teens, all because they are getting more of the extra sleep they need.

In Fayette County, Kentucky, crash rates of teenage drivers dropped 16.5 percent in the two years after start times were delayed one hour (which happened 10 years ago), compared with the two years before the change. Data provided to Sleep Cycle by teens who use its smart-phone app indicate that those who get less sleep have greater levels of stress than those who sleep even just a little longer.

What’s more, communities find that the usual worries about starting school later do not pan out, according to an analysis by the National Sleep Foundation. Students still succeed in holding part-time jobs, and after-school programs such as sports and theater still run well.

“I get tired of the argument that these kids have to do all these activities and community service and therefore can’t start school later,” Wahlstrom told me for a story I wrote on this topic last August. “The issue is not the start time,” she said then. “It’s that the students are overly busy. There is too much pressure to cram it all in just to have a good resume to get into college.” Students, parents and school advisors should all be more judicious with what students choose to participate in, she said, with emphasis on doing certain activities well rather than compiling a long list.

Photo courtesy of Send Me Adrift on Flickr