From Slate by Russell Foster:
The biology of human sleep timing, like that of other mammals, changes as we age. This has been shown in many studies. As puberty begins, bedtimes and waking times get later. This trend continues until 19.5 years in women and 21 in men. Then it reverses. At 55 we wake at about the time we woke prior to puberty. On average this is two hours earlier than adolescents. This means that for a teenager, a 7 a.m. alarm call is the equivalent of a 5 a.m. start for people in their 50s.
Precisely why this is so is unclear, but the shifts correlate with hormonal changes at puberty and the decline in those hormones as we age….
Sleep is not a luxury or an indulgence but a fundamental biological need, enhancing creativity, productivity, mood, and the ability to interact with others.If you are dependent upon an alarm clock or parent to get you out of bed; if you take a long time to wake up; if you feel sleepy and irritable during the day; if your behavior is overly impulsive, it means you are probably not getting enough sleep. Take control. Ensure the bedroom is a place that promotes sleep—dark and not too warm—don’t text, use a computer, or watch TV for at least half an hour before trying to sleep, and avoid bright lights. Try not to nap during the day and seek out natural light in the morning to adjust the body clock and sleep patterns to an earlier time. Avoid caffeinated drinks after lunch.
It is my strongly held view, based upon the evidence, that the efforts of dedicated teachers and the money spent on school facilities will have a greater impact, and education will be more rewarding when, collectively, teenagers, parents, teachers, and school governors start to take sleep seriously. In the universal language of school reports: We must do better.