10 pm / 11 pm at the latest if with an organized group, such as church youth group. As for just hanging out - not giving me any real plans as where and who they'll be with it's home by 9pm. Like the movies is over at 9:30, that's when the 10pm would be okay.
My kids curfew is determined by what their plans are. They are not allowed to just "hang out" unless I know where they will be and who they will be with. I like for them to be home by 11, but if they go to a late movie that's not reasonable.