What time do you sleep at?

Well I have school, and need to wake up at 6:40 AM, so I normally go to sleep at 10 - 12 but recently I've been sleeping at 2 AM playing on my PC and it really messes me up while at school, and this is just on Weekdays.
On Weekends, I go to sleep whenever usually 2AM - 3AM unless I fall asleep before.