My niece is 16, and regularly posts on FB at 4am or 5 am saying she's just off to bed, or that she really must get some sleep now, etc.
She's always been allowed to stay up late, and SIL has always stayed up untill midnight/1am .
She's home educated, and an only child, so has no need to get up early the next day, but I can't help thinking this isn't healthy, or good preperation for working life...unless she gets a job working nights;then it would be perfect.