Adolescent circadian rhythms shift naturally towards later sleep and wake times. This is biological, not laziness. When school schedules force early rises, chronic sleep deprivation follows. Sleep debt in teenagers is associated with worse academic performance, higher injury rates, and greater risk of mental health problems.
Screen light in the evening suppresses melatonin and delays sleep further. A phone curfew 60 to 90 minutes before the intended sleep time, combined with keeping the phone outside the bedroom, consistently improves both sleep onset and duration.