Most 12 year olds are annoying. Their voice is annoying, especially when they're armchair commanders who think they're pro and the team captain or something. I played games as a 12 year old, sure, but not online and certainly not with a mic.
When I was that young, I played Guild Wars but was in an adult guild because I showed them I was mature enough to be with them. I am way more accepting of younger players if I actually get to know them, or do know them already, just like my Guild Wars guild did with me.