How Old Should Kids of the Opposite Sex Be Allowed in Bathrooms?

I had really never thought about this before a month ago, but I gotta say something. My family and I were enjoying a weekend at The Great Wolf Lodge near Seattle which is really cool by the way, but what happened in their changing room was not so cool.

My wife, her mom, and my daughter were changing and across from them was an 8-10 year old boy staring at them. My wife described it as a freaky kind of stare, like he was enjoying it. It made them really uncomfortable and they passes around towels and tried to cover themselves the best they could. That kid is lucky I didn't hear about that until later or his parents and I would have had words.

Is is just me or is that waaaay too old for him to be in the women changing room. Do his parents realize they are probably turning him into some kind of sexual deviant? I feel that there should be an official age of 5 or under for the opposite sex in changing rooms and bathrooms, after that age they can go to the bathroom on their own. Who is with me?