More than 40 percent of the nation's public high schools start classes before 8 a.m., according to government data cited in the policy. And even when the buzzer rings at 8 a.m., school bus pickup times typically mean kids have to get up before dawn if they want that ride.
"The issue is really cost," said Kristen Amundson, executive director of the National Association of State Boards of Education.
School buses often make multiple runs each morning for older and younger students. Adding bus drivers and rerouting buses is one of the biggest financial obstacles to later start times, Amundson said. The roughly 80 school districts that have adopted later times tend to be smaller, she said.
After-school sports are another often-cited obstacle because a later dismissal delays practices and games. The shift may also cut into time for homework and after-school jobs, Amundson said.
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The policy, aimed at middle schools and high schools, was published online Monday in the journal Pediatrics.
Evidence on potential dangers for teens who get too little sleep is "extremely compelling" and includes depression, suicidal thoughts, obesity, poor performance in school and on standardized tests and car accidents from drowsy driving, said Dr. Judith Owens, the policy's lead author and director of sleep medicine at Children's National Medical Center in Washington, D.C.