My son is 10 yrs old. Last yr. he was in 4th grade and went to bed at 8:30. This school yr. we might try him out at staying up until 9:00. He is the type of child that needs to get a lot of sleep to be able to get up and function in the morning. He needs a good 8 hrs. of sleep each night or he is a bear.
I think that it would depend on your child and whether or not he can handle staying up a little later or not. Kids that age still need their sleep, though, and I wouldn't allow any later than 9:00.
I remember when I was 15 that I was allowed to stay up until I wanted to go to bed. Now, being that I was responsible, I would always go to bed by 11:00, if not earlier. Again, I think that it would depend on how your child can handle staying up and getting up the next morning. I'm sure we have members with older children who can give some better advice.
My 5 yr. old is starting kindergarten this year so this will be the first time that she will have to go to bed by herself with her brother staying up later. I am not looking forward to that battle!