Hi - Good luck on your meeting tomorrow. Others have given great advice, and I don't have much to add, except to comment that the excuse for keeping your DS from moving out of 3rd grade math sounds pretty flimsy and those reasons could be caused by the fact that he's being given inappropriate work. If he's already done the 3rd grade stuff 2 years ago, he's not going to be too enthused to show his work, be neat, or follow directions, I would imagine.
I would second the exploration of online math programs like EPGY or Aleks, if a real person teacher is unavailable. Those programs work at a student's individual level, and so are sometimes a great alternative.
