According to the Los Angeles Times, there may be a biological reason.
A study at Brown University suggests that teenagers can't wake up early because their bodies haven't finished developing and growing.
Everyone needs melatonin in their system to fall asleep. And teenage bodies produce melatonin later at night, so they still have it in their system in the morning, and find it harder to wake up.
Schools that start at 7:30 or even earlier, find their classes filled with sleepy students who can't pay attention. And tired teens are more likely to have behavior and drug problems, negative moods swings and out-of-control emotions.
In the past ten years, school districts in 20 states, including Alaska and Florida, have refused to start classes before 8:30 a.m., particularly in schools that aren't performing well on standardized tests. It's hard to tell whether grades are getting better, but the number of dropouts has fallen about 3% a year.
At one school, 50% of the students who were late every day now get to school on time.
And teachers think their students are more awake and better able to concentrate before lunch.
And what's the final benefit of starting school later in the day? The teachers get to stay home long enough to have breakfast with their own kids.