In the book Nurtureshock (must read for any parents, IMO), sleep deprivation is considered as #1 cause for all evils. Many schools forces teenagers to wake up as early as 6AM and they typically can't go to bed before 11Pm. This is loss of 2 hours of sleep each day for brains that are still developing. Result is colossal drop in grades along with other artifacts. Schools do this to accommodate different grades in same building. Lot of schools have fixed this slightly after this book came out by making teenagers start late and kindergartens start early.In my view, it should be unlawful to have schools start before 9AM for any grades.