Generally I have very bad insomnia if i try to go to bed at a set time or if I'm not at the point of passing out from exhaustion - every day I get in bed around 2300 already dead tired and only end up falling asleep at 0500 or close to that. For this reason I had to find a job that would normally be considered bad work hours - it started at 0230 and ended at 0600, luckily this was very easy for me to find because the company operates mainly in my area and had a shortage of staff. It hasn't affected me so badly considering a job, but I really never see my friends anymore because I sleep during the day and wake up as the sun is about to set.
At school I never really had a problem with sleep because I stayed active and came home tired enough that I could even take a 2 hour nap and still be ready to sleep at 2200.