It really depends on the person. There's a 7 year old I play with, and he's very good. It's unfortunate that he's afraid to join party chat because no one wants to play with a squeaker. But some kids can be pretty annoying, always blaming everyone else when something goes wrong and not listening to the rest of the team. Another problem with younger players is that some of my regular teammates and I like to talk about more "adult" subjects, and we feel a little weird doing that with kids listening. We usually just adopt the mindset that it's their problem if they want to play with us, though.