According to research, from SRI International, youngsters who go to bed early, at the same time every night, turn out more intelligent.
(In the study, children who had regular bedtimes were better at languages, reading and maths than those who did not, and the earlier a child went to bed the quicker they are at picking things up. Maybe parents should punish their children by making them stay up late, rather than sending them to bed early.)
Source: http://www.dailymail.co.uk