PITTSBURGH (AP) — As darkness faded just after 7 a.m. Friday, sleepy high school students across Allegheny and Westmoreland counties stood at bus stops or steered vehicles to school.

Others already were inside on the way to breakfast or study halls, while others were beginning their first academic classes of the day.

Districts in and around Pittsburgh, including some whose first bell rings at 7 a.m., are evaluating daily schedules as research and day-to-day experience make it increasingly clear that later start times could benefit students' mental health and academic success.

"What we're worried about is when you really start to look at the stress, it leads to things like depression, it leads to things like suicide, it leads to risk-taking behaviors," said Robert Scherrer, superintendent in the North Allegheny School District. "And some of those are tied directly to sleep, in some cases, but they're also mental health concerns."

The Centers for Disease Control and Prevention recommends that middle and high schools start at 8:30 a.m., along with 8.5 to 9.5 hours of sleep each night for adolescents.

North Allegheny began considering later start times last year. The district made headlines last week following two public community forums intended to inform and consult parents and staff on the matter.

The district starts first period classes at 7:25 a.m. and dismisses students at 2:15 p.m.

What happens in the first minutes of the school day varies from school to school. Many districts offer breakfast, activity periods or study halls before the first academic period of the day. For that reason, the Tribune-Review used the first academic period of the day — which typically lasts about 40 minutes — as a point of comparison of start times.

For example: Though Hempfield Area High School has the latest first period start time of the 34 districts surveyed, students are required to be present for a mandatory study hall starting at 7:35 a.m., Principal Kathy Charlton said. During this time, some students participate in tutoring or clubs. Those who are not involved in extracurricular activities must still be present for the study hall because attendance is taken, she said. First period academic classes at the school start at 8:25 a.m.

Coming to school after sunrise could be having a positive impact on students at Avonworth High School, which this year shifted its Period 1 start time from 7:15 a.m. to 8 a.m.

"Talking to our kids, they are much happier and feel like they are much better prepared coming into school," said Thomas Rolston, superintendent at Avonworth.

Rolston said the district has not seen changes in attendance since shifting start times. Tardy arrivals have remained consistent and could be chalked up to poor time management — students chatting too long with friends before heading to class, for example.

Experts say there's merit to these observations.

"We know that sleep, just for humans in general, has an impact on almost all areas of our functioning," said Jessica Levenson, assistant professor of psychiatry at the Children's Hospital of Pittsburgh.

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POSITIVE RESULTS

Not getting enough sleep could impact the ability to pay attention or execute tasks that involve planning or organizing, she said. Some studies also show that lack of sleep could be associated with risky behaviors or ability to get along with others.

And if it seems like a teen is just being difficult about getting out of bed in the morning, there's a case for blaming biology: The body's circadian rhythms are delayed during the teenage years, which means young people going through puberty naturally want to go to sleep later and wake up later, Levenson said.

"It's part of the reason why, I think, these super early school start times work against what their bodies want them to do," Levenson said.

In 2014, the American Academy of Pediatrics urged middle and high schools to start no earlier than 8:30 a.m. to ensure students get enough sleep and maintain healthy sleeping habits.

Since then, several organizations and school districts across the country have made similar recommendations.

One such study conducted by researchers at the University of Minnesota Center for Applied Research and Educational Improvemen t found that later start times correlate with increased academic performance for high school students.

Tardiness, substance abuse and depression also dropped, according to the study.

Districts set their own arrival and dismissal times, but all Pennsylvania schools are required to be open for at least 180 days of instruction. Secondary schools must offer 990 hours of instruction, according to the Pennsylvania Department of Education.

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TACKLING OBSTACLES

Logistics and budget concerns, particularly those related to school bus arrival and departure times, present challenges to making changes to the school schedule.

That's the case in the Woodland Hills School District, where high school students begin first period classes at 7 a.m. The school has one of the earliest first period start times in Allegheny County.

The district was moving toward a later start time last year but put changes on hold as leadership issues at the high school were resolved, Superintendent Alan Johnson said.

"We absolutely want to do it," Johnson said of moving to later starts, adding that the challenge lies in determining how to add buses needed to run more routes without breaking the bank.

Like many districts, Woodland Hills uses the same buses to transport students at schools throughout the district. Making high school start times later could mean adding about 25 more buses, which would cost the district hundreds of thousands of dollars, Johnson said.

Woodland Hills uses 120 buses to transport 7,200 students to 92 locations each day, with 3,850 students traveling to schools within the district and 3,350 heading to charter and private schools.

North Allegheny transports over 8,300 students across the district's 49 square miles each day. Buses make trips to about 40 different school locations and transportation accounts for about $6 million of the district's $157 million budget.

Adding buses could add $1 million to the transportation budget, Scherrer said.

Buses begin arriving at Norwin High School in Westmoreland County shortly after 6:45 a.m. Students can go to the cafeteria and get breakfast before heading to homeroom at 7:13 a.m. The first period bell rings at 7:38 a.m.

Though the district is not considering later start times, Assistant Superintendent of Secondary Education Timothy Kotch pointed out that any changes would trickle down to the elementary schools and impact afternoon extracurricular activities such as sports practices and clubs.

The district serves about 5,250 students.

"If we change our dismissal time at 2:16 p.m., that's going to push everybody back however many minutes we would change," Kotch said.

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Information from: Tribune-Review, http://triblive.com