What is an appropriat bed time for a 5 year old boy?

We have a 5 year old son who is in preschool. His dad has been putting him to bed at 8pm, and I think that this is way to early for him. When he goes to bed at 8, he wakes up early (we're talking 5:30) and is ready for the day. I tried to talk to him (his dad) about extending his bed time to at least 9pm, but he disagreed. When our son goes to bed later, he does sleep longer (at least until 7-8am) Just wanted to get kind of a tally of what time other 5 year old boys go to bed, Thanks!