Teenagers are not being lazy: their body clock really does shift one to two hours later

Melatonin starts arriving closer to midnight while school still starts at eight, and that gap is chronic sleep loss rather than defiance.

Three things work: bright light in the morning, limits on screens and light in the evening, and a fixed wake-up time instead of sleeping half of Saturday away. They need 8-10 hours; under seven shows up in grades, mood and how often they get ill.