Just interested, really. DS has few problems with other kids, and has great friends. However, every Saturday he plays a racquet sport and three boys of his age, all around the same standard as DS go sometimes and when they do, they all sigh when DS misses, and give each other meaningful looks, talk down to DS, have in the past said how rubbish DS is and things like "you aren't going to miss that shot are you?" (though coach put a stop to that, it is all a bit more subtle now). They ignore DS if he talks to them, and are generally exclusive. DS generally plays to an equivalent standard as them. There are other kids of different ages in the same group, and when these three boys are not there, which happens around every other week, the atmosphere is completely different, very friendly, fun and good natured.
I just wondered how your 13 year old would react to the three boys, as I say, just interested, and looking for ideas.