Fair to say that getting to bed earlier and practicing good sleep hygiene could help a lot of kids sleep longer and better, and so your suggestion would benefit some. But a lot of kids (especially teens) have circadian rhythms that just don't mesh with early school times. In these cases, getting them to be earlier won't solve the problem—their bodies are not primed for sleep early enough. Just ask any an adult night owl who tries to go to bed earlier and spends a few hours staring at the ceiling. It's indeed a complex problem, and later school start times can be a significant part of the solution.