I usually sleep for about 6-7 hours a night because I have to get up at 5:40 every morning to be able to get my bus on time (I live pretty far away from my school). I'm always tired though, and try to make up for it on weekends.
Scientifically speaking, teenagers need more sleep than in any other stage of life except for infancy. It's been said that teenager's brains don't actually function properly until around 9am. Like someone else said, power naps are ideal from around 12pm-3pm. Obviously school/work doesn't cater for this, sadly. Studies have shown in the US though that when a school's start and finish times are moved back by about 2-3 hours (for example, if you began at 8am and finish at 2pm, your new start time would be 10 or 11am and your new finish time would be 4-5pm) student's performance levels increase dramatically.
So school start times are pretty stupid when you think about it, and aren't designed for maximum performance from students- it only hinders us.
So yeah, if your parents tell you that you are lazy or disobedient for not feeling tired at 11pm and/or not wanting to get up until 9:30/10am, read up on teenager biology and prove them wrong, hahaha.