No later than 10:30 on a school night. If they have to go to bed at 7:30, 9:00 or 9:30 would work. Or, perhaps, by 9:00 they have to be in bed and they can read quietly until 9:15 or 9:30.
On weekends, 11:30 should be max (with midnight for special occasions); but the time before can be allotted whether the child has behaved, etc. and is based on the parents' discretion.
I think that a normal bed time for an 11 year old is 9:30 or 10:00
7:00
8.30
Between 9-10pm.
8pm
8:30PM
11:00pm
8:30 or 9:00pm
9pm-10pm
10:00 p.m.
8:30 or 9 PM
about 7:15