Bedtime since we (my brother and I) were in prep, or 5years old or therabouts, was 8-8:30pm.
It had been 7-7:30 but mum had trouble getting us to go to bed or stay in there, and found that by putting it back a little was much more conducive for us to get to sleep.

A lot really depends on the child though, a friends kids go to bed at 7-7:30 and 90% of the time they will still be awake at 10or 11 at night