Since his school is large, is there any chance you could get him switched into a different teacher's same-grade class asap? It's not the answer for the long term, but it sounds like his current teacher is a *really* bad situation for him. Our own ds had a similar situation with his 2nd grade teacher - rather than acting out in school he withdrew and was having panic attacks... it was recommended to us to switch him to a different classroom, and we found that putting him a new room with an entirely different teacher who had no preconceived notions about our ds and no past history with us (parents) made a huge (and very positive) difference for our ds.
You'll still need to advocate for more challenging work / gifted services etc - but it sounds like you have a very basic situation that needs resolving asap.
I'm so sorry your ds is in this situation - how frustrating!
polarbear
