Studies have repeatedly shown that teens go to bed around the same time no matter what time they have to wake up.
Biology is the reason, not choice. During those ages their circadian rhythm is set a few hours later.
It generally changes as we age to going to bed earlier and waking up earlier in the morning.
In humans evolutionary history, we've almost always been around large nocturnal predators. Having staggered sleep cycles that allow some members of the group to be awake and on guard is and important adaptation.
In today's society with our strict time schedules, it's a maladaptation.
I think an important part of the conversation is that most teens have a different circadian rhythm.
Ideally, the schools start late enough that teens can go to bed at midnight or 1 AM and still have enough time to get the sleep they need. Instead of school ending at 2 or 3 o'clock in the US, why not end at 5pm and make the start time later?