It might be the parents' computer, but honestly, restricting kids' access to it is like having a huge bowl of candy in the room that they can never touch. As a kid who was once restricted use, I can say that it's really easy to get frustrated. Controlling things like a curfew or which friends you are allowed to hang out with is fine, but when the computer is in the home and there are ways to check what kids do on the computer, restricting it is just kind of ridiculous in my opinion.