It’s 8:35 a.m., the start of first period at Park High School in Cottage Grove, and despite an overnight snowfall that slowed traffic, the scene is serene. No mad rush, no elbows flying in the hallways, just three late students stepping through the front entrance on their way to class — and only one of them running.

Five years ago, when the school day started an hour earlier, many students here would be just emerging from the fog of first hour. They would hope to be past the yawns and rubbing of eyes from the lack of sleep, and finally on track for the rest of their day.

Since that time, the South Washington County School District has joined other districts locally and nationally in moving to align school start times with teenage body rhythms. A before-and-after review of the district’s three high schools showed tardiness on the decline, and more important, academic performance on the rise.

Those results — part of the findings of a University of Minnesota study released last week — have caught the attention of parents and school leaders in the St. Paul public school district, which now is giving a closer look to possible start-time changes in one of the state’s largest school districts.

“I really like the start of our high schools,” South Washington County Superintendent Keith Jacobus said Wednesday. “It’s relaxed. It’s calm. Kids can really take control of their study time. They can socialize. When it comes to that first hour, they’re primed to learn.”

In 2009, South Washington County followed the lead of a growing number of school systems in deciding to delay high school start times in the belief that students perform better if they sleep longer. Given the timing of the district’s action, it came as little surprise that among students interviewed Wednesday at Park, no one could speak to what life was like with a 7:35 a.m. start.

Students filled the hallway at Park High School before the start of their first hour class Wednesday, March 18, 2014, in Cottage Grove.

But they did point to the perks of starting the day later — the ability to work later hours at part-time jobs or to study deep into the evening.

Brandon Trisko, a senior, has a retail job with a shift that lasts until 10 or 11 p.m. several nights a week. That would not be possible with an earlier start time because the late hours would cut into his sleep, he said.

“I would have to ask to leave work early or to have a shorter shift, and I don’t think my manager would allow that,” he added.

Eric Brinkoetter, also a senior, said he arrives at school 45 minutes early each day because his mother, Kim Brinkoetter, drops him off on her way to work.

“It’s a good chance to catch up with teachers if you missed something the day before or [need to] do homework,” Brinkoetter said.

A change for St. Paul?

In St. Paul, Superintendent Valeria Silva said this week that she had received many e-mails citing the benefits of later high school starts. But because the district — the state’s second largest — has a complex busing system, the idea and the potential cost need more study. The school board, however, could see a recommendation on the issue this fall, an administrator said.

“Once you move, or if you move, the older kids to a later time, it affects the whole system,” Silva said. “Anytime you put a bus on the street there’s a cost.”

Jacobus took over in South Washington County in 2012, several years after the start-time changes, which he described as “cost neutral” for his district.

In the 1990s, while a principal in Colorado, Jacobus took note from afar when Edina High School became one of the first in the nation to adopt a late start. But he couldn’t persuade his district to make the move.

“I seemed to have a lot of morning people on the faculty when I was principal,” he said.

A former biology teacher, Jacobus is fascinated by brain science. Last October, he attended a conference about teens and sleep at the University of Minnesota. Later, he arranged for Kyla Wahlstrom, a university researcher who has studied school start times for 17 years, to review with South Washington County board members what occurred in the district before and after the move to later high school start times in 2009-10.

First, the science:

Wahlstrom has promoted later start times for high schoolers, in particular, because she says the teenage brain develops differently than an adult or prepubescent brain.

For teens, the idea of going to bed early to wake up early doesn’t work, she said, because their bodies don’t experience a natural shift into sleep until 11 p.m. — no matter when the school start time might be. So the later the start, the better the chance of having a student in class ready to go.

Now, the findings:

Park High School seniors, from right, Brandon Trisko, Eric Brinkoetter and Nathan Grosse like their school’s later start time. Trisko said it helps him get enough sleep on days when he works until 11 p.m.

• Performances on state standardized math tests rose at the South Washington County high schools, as did student grade-point averages, she said. (There were no significant changes in state reading test results.)

• About 59 percent of high school students surveyed said that they averaged eight or more hours of sleep.

• The total number of crashes involving 16- to 18-year-old drivers in Cottage Grove and Woodbury fell from 144 to 135, a 6 percent decline.

Of concern to Jacobus was a survey finding indicating that 88.5 percent of students went to bed with a cellphone in the room, a potential disruption that has led him to suggest to parents that they try to keep their teens away from electronic devices for about an hour before bedtime.

Kim Brinkoetter said that she is pleased that her son, Eric, manages to get eight hours of sleep, especially at a time when it’s so easy for students to stay up late messaging one another.

But, she added in a reference to the age-old struggle between parents and headstrong teens, “honestly, I don’t think it matters what time you tell a teenager ‘It’s time to go to bed.’ ”

Park Principal Kerry Timmerman, who taught and coached previously at Harding High in St. Paul, said that he could see the St. Paul district moving to later start times. He spoke, too, of remaining in contact with friends still working at Harding, and of kidding them about their ability to leave school at 4 p.m., when he still is on duty.

“I tell them that they’re slackers,” he said. “Of course, they have to get there earlier.”

Callie Sacarelos is a University of Minnesota student reporter on assignment for The Star Tribune.