In my day,, the local district started school at 9am and let us out at 3:30 pm. These days I see kids waiting for the school bus at 6:30 am, but I think they go home around 2 pm. Not sure about other districts, but I believe the class hours here are set by the teachers union. They want to start early, so they can go home early. There is also the matter of bussing. In the old days, a kid went to the school up the street. Now they are bussed to a school across town. Neither the parents nor the kids have any say in where the kids go to school.
Is the early start a bad thing? I don't know. It does prepare the kids for the real world when they have a job that requires them to start early. And a simple solution to not enough sleep is for parents to turn off the computer and video games and compel the kids to go to bed at a decent hour. On school nights, I was in bed by 9 pm. These days I see kids roaming around the streets at all hours. No wonder they are tired the next day.