The school district for Cumberland and North Yarmouth joined a growing national movement this week when its board of directors approved later start times for students.

The 6-3 vote, taken Monday evening by School Administrative District 51’s board of directors, will affect more than 2,000 students at Greely High School, Greely Middle School and the Mabel I. Wilson elementary school. The later start times will take effect when the 2016-17 school year begins Aug. 31, according to a letter posted Tuesday on the district’s website by Superintendent Jeffrey Porter.

Students at Greely High School will begin their school day at 8 a.m. instead of the current time of 7:30 a.m. They will be released at 2:30 p.m. instead of 2:12 p.m.

Greely Middle School students in grades six through eight will start classes at 8 a.m. instead of 7:33 a.m., and will be dismissed at 2:33 p.m. instead of 2:15 p.m.

Students in kindergarten through fifth grade will begin class at 8:45 a.m. instead of 8:30 a.m. Their dismissal time will be 3:15 p.m. instead of 3 p.m.

Porter said the new schedule means that the school day at Greely High School will be 12 minutes shorter, but he added that instructional time has been preserved and will not be reduced. That also applies to grades six through eight at the middle school, where a student’s school day will be shortened by nine minutes, but instructional time won’t change.

Changing over to a block classroom schedule in the fall will allow the high school to protect instructional time, but will also mean fewer daily classes for students. Each block classroom – four per day – will last 84 minutes, replacing the seven 50-minute-long classes now. Grades six through eight are not being changed to a block schedule.

The length of a school day for students in grades K through five will not change under the new schedule.

Though there will be fewer classes each day for students in the higher grades, students will still be able to choose from a variety of course options. Porter said with fewer classes, students may receive less homework.

“I am confident that this change in start times is in the best interest of our students and I am pleased that our district has made this important shift in line with indisputable research supporting this change,” the superintendent said.

Several school districts in Maine are considering later start times based on recommendations by the U.S. Centers for Disease Control and Prevention that early start times are detrimental to students’ health. School boards in Saco, Biddeford, Old Orchard Beach, Thornton Academy in Saco, Scarborough, South Portland and Yarmouth are considering changing start times.

Cape Elizabeth and Falmouth have already adopted later start times for their schools, consistent with those approved by SAD 51.

The district formed the 18-member Late Start Committee in September to study the concept of starting school later for secondary-grade students. The study determined that students in kindergarten through fifth grade would also have to start school later to accommodate busing schedules.

Porter said a community survey filled in by more than 1,300 people showed that an overwhelming majority of Cumberland and North Yarmouth residents supported later start times. Eighty-six percent of students and 83 percent of parents and staff members who responded to the survey favored later start times.

The CDC recommends that middle and high schools start classes no earlier than 8:30 a.m. According to the latest available CDC report on the topic, Maine’s average high school start time is 7:53 a.m., 10 minutes earlier than the national average.

“We would have liked to have gone for 8:30, but there were other pressures that we had to consider,” Porter said Tuesday evening.

Porter said the board did not want to interfere with older students’ after-school activities such as sports and jobs by going with an 8:30 a.m. start time.

“Pushing back school to 3 p.m. would have been detrimental for some of our older kids,” he said.

Numerous research studies have demonstrated that early starting times are harmful to teenagers’ health because the developing brain is wired differently from an adult’s. The CDC said teenagers need more sleep than adults – at least 8½ hours compared with seven hours for an adult. Starting school too early has led to higher rates of health problems, including obesity and depression, and has been shown to lead to more frequent car accidents caused by drowsy teenagers driving to school.