With research suggesting a variety of benefits of later high school start times for students, some Twin Cities area schools have begun to push back start times, while others have decided against the change.

For Wayzata Public Schools, a December 2015 school board vote in favor of shifting to later high scool start time, among other changes, was unanimous. One month earlier, St. Paul Public Schools' board voted to not change start times, while participating in a pilot at one school in an effort to test a later start.

Feasibility and potential health benefits were key issues for both school districts.

Research has shown the benefits of later start times range from improved academic performance to a reduction in student car crashe. A 2014 study from the University of Minnesota, which studied more than 9,000 students from eight public high schools in three states, found that shifting school start times to 8:55 a.m. from 7:35 a.m. decreased car crashes for teen drivers (ages 16 to 18) by 70 percent.

"The evidence is really clear that later start times are incredibly beneficial for academic outcomes, school attendance, mental health, and injuries — specifically car crashes," said Rachel Widome, assistant professor of epidemiology and community health at the University of Minnesota.

Studies show nearly one-third of American teenagers get at least eight hours of sleep each night. The American Academy of Pediatrics recommends teenagers between ages 14 and 17 get 8.5 to 9.5 hours a night.

In Wayzata, the research was persuasive enough to lead the school board to unanimously adopt nearly an extra hour of sleep for high school students. The start time went to 8:20 a.m. from 7:30 a.m. for the 2016-17 school year.

For Wayzata Superintendent Chace Anderson, the later start was necessary, despite opposition from some parents who worried about the effect on elementary schools, which would start earlier to provide available buses for high school students later in the morning.

"Research shows that they wake up bright-eyed, bushy-tailed and ready to go," Anderson said of elementary school students. "Whereas for high school kids, it's a little harder to get the engine going. So we have elementary teachers saying kids are tired by the middle of the afternoon and high school teachers saying students aren't awake until 9 a.m."

The Burnsville-Savage-Eagan district also pushed back its high school start time for the 2016-17 school year. Minneapolis and Edina schools switched to later start times several years ago. Schools across the nation also have followed suit.

In Wayzata, the most straightforward approach was to simply rearrange bus schedules. Anderson said the district's 85 buses are enough to transport more than 10,000 students over a staggered pickup and start time schedule.

St. Paul Public Schools doesn't have the same luxury. By serving more than 39,000 students, St. Paul district bus drivers have a lot of ground to cover.

Similar to Wayzata, St. Paul schools use a three-tier system in which buses drive multiple routes on a staggered schedule. In the current system, high school and middle school students are picked up first, followed by elementary students.

To accommodate an earlier high school start time, elementary students would have to start school earlier or the district would have to increase transportation resources for students, at the cost of about $8 million, according to Jacqueline Statum Allen, assistant director of strategic planning and policy at St. Paul Public Schools. Metro Transit could help fulfill part of that added service, but it would be able to pick up only part of the slack. The remainder would have to be covered by the district, which already has a $15.1 million budget deficit for this school year.

"Anywhere that we are moving high school students without moving an equal number of elementary school students, that would cost us money," Statum Allen said, "and we would rather have money in the classroom, not in buses' gas tanks."

Despite those challenges, the district will continue a pilot program at Johnson High School, which began last year with a shift to an 8:30 a.m. start time and the use of Metro Transit buses. The district is working with the University of Minnesota to study the effects of the pilot, according to its website.

The chance of restarting the conversation for the entire district is still possible, Statum Allen said.

"I think it would be time to talk about it again maybe starting next spring, which would be changes then for the 2018-19 school year," she said.