How does a parent approach such a kid and get through to him?
By getting him into a setting where differentiation is happening less overtly and more inclusively, I'd think.
Otherwise, he's going to keep doing what he's doing. Who wouldn't? It sounds as though he's well-liked by his peers, if not as much appreciated by the adults in charge. Sure, he's that trouble-making kid, but those kinds of kids hold a definite allure for their peers, believe me...
at six, this in and of itself doesn't sound so immature to me. It sounds to me as though he's highly social, maybe a little lonely (no siblings, perhaps? no neighbors to play with at home?) and is well-equipped to solve those problems and alleviate his boredom at the same time.
My son's teacher sends me notes that he is a distraction and a disruption. She acknowledges that he is gifted and that he is super bored and that he is a superior multitasker who can finish his tasks without completely focusing on what he is doing. She has asked me to send in a work packet from home if I wanted to challenge him
Wellllllll... this teacher may be the nicest person on earth, but she's asking YOU to do her job for her and to manage a classroom problem.
I wouldn't do it. If she sees that he needs differentiation, then SHE needs to be the one going to bat for him. If she
knows what the problem is (and it sounds like she does) then why isn't SHE differentiating work for him in ways that don't make him stand out from his peers? He obviously has great leadership qualities and has a high need to belong to the group.