Schools also have to take bus schedules into account. A district with elementary / middle / and high school will have 3 separate bus schedules if there's enough population.

My 8 year old nephews' school day doesn't begin until 9:40, but it ends after 5pm and allows very little sunlight for play time in the evenings. I know that when I was that age, I was far more concerned about being able to go out and play than whether the sun was up when I got up.