No need for school to start at the absolute butt-crack of dawn. It's actually been shown to be harmful for teenagers. Their natural sleep cycle involves sleeping in. Many of them simply physically cannot function so early in the morning. (Thinking is a physical process...)
If high school started an hour later, the kids would be on the streets less while parents are off work, too. So it seems like a win-win, without actually increasing the number of hours of instruction.
Increasing the duration of school won't automatically improve education. "No Child Left Behind" certainly didn't, but it did require greater duration to the school day if you actually met all of its requirements.