Is 7 hours of sleep enough for a 15 year old guy?

I have to wake up at 6 every morning for school. I usually try to get to bed by 10:45, but sometimes it just doesn't happen. On weekends, I just can't sleep in. I go to bed at 2 a.m. latest and then I just wake up again around 7 maybe 8. Am I getting enough sleep to grow?