I'm sure more people will respond but I would say, in my opinion, I'd agree that your son should definitely not be at the meeting. Why do they want him there with all those adults? Wouldn't that make him more freaked out (anxious) and cause his behavior to become worse? That's what I would think.
I'd also find out if the frustration is, right now, concentrated on the times of day when he would be more underchallenged. (Such as, For a bright math student, filling out mind-numbing math sheets).
As an adult have you ever felt bored day after day and had your intelligence insulted, add that too being more emotional than "average" and trapped with alot of peers you can't relate to? ...trying humor was a normal response for a boy his age, but if the teacher is getting angry in response your son is matching that?
Do you have any samples of what he is capable of doing, math-wise, that you can bring from home?
Good luck, I think you're somewhat in good company in this forum.
