In recent years, American teens have earned less than stellar scores on a national exam administered by the U.S. Department of Education. On the National Assessment of Educational Progress ― also called the Nation’s Report Card ― only about 34 percent of eighth-grade students scored high enough to be deemed proficient in reading in 2015. Only about 33 percent scored proficient or above in math.

A new analysis from the Center for American Progress argues for one simple step to help raise these scores: Start school later in the day.

Delaying start times by an hour across the country could boost students’ math scores up to eight points on the Nation’s Report Card, the analysis says. That’s almost one grade level of learning. The idea is that giving sleep-deprived teens more time to snooze before they hit the books will help them learn better.

The Center for American Progress researchers drew on a previous study out of Wake County, North Carolina. In that study, released in 2012, middle school students who switched schedules to start school an hour later saw their test scores increase. Low-performing students saw the biggest boost.

The Center for American Progress considered what would happen if those results were repeated around the country.

“What we found is the impact on student achievement would be quite large,” Ulrich Boster, a senior fellow at the center, told The Huffington Post. “Starting schools later could dramatically improve student outcomes.”

There are limitations to this analysis, the researchers concede. They made the assumption that the gains on North Carolina’s tests could be reproduced on the National Assessment of Educational Progress, even though the exams differ. Also, much of learning improvement in the Wake County study came from schools that had been opening notably earlier ― at 7:30 a.m. ― than many of their counterparts around the country do.

“The rest of the country isn’t necessarily like North Carolina. There are all sorts of other variables that could confound. But given the huge suite of research we’ve seen on the power of sleep ... there’s no reason we wouldn’t see a big impact by having schools start later,” said Boser.

Most American students are severely sleep-deprived. Teenagers average about seven to seven-and-a-half hours of sleep a night, even though doctors recommend they get about nine hours. Hormonal changes in teens tend to keep them up late.

Some public school districts, like Seattle, have taken strides to delay start times in the interest of student health. But others have actually moved to make start times earlier, Boser said. Although the American Academy of Pediatrics recommends that schools start after 8:30 a.m., the average start time for middle and high schools around the country is 8:03 a.m., according to an analysis from the Centers for Disease Control and Prevention.

Schools may be keeping start times early so that kids can engage in extracurricular activities later in the day. Delaying bus schedules for students can also be logistically difficult, said Boser.

But this is the bottomline, he said: “If we prioritize student outcomes and student achievement, we would see a lot of benefit by shifting these times later.”