1. They know they and everyone else will just stay up later. 2. School will go on too late in the day, sports participation is dropping appreciably. 3. Those who work after school or school/sports are quitting sports to work, and planning ways to leave when they did previously to go to work.
This is incredibly short-sighted, and will not last a year.
Anecdotally, when I was in high school, with a 7:30 AM start, around 25% of the class was asleep through 1st period. And this was in honors/AP courses with the kids who wanted to learn, get good grades, and generally be successful.
So my anecdotes don't match your's.
