Welcome to the boards.
Whether it is a gifted thing, a personality thing, or something else, it would seem the more controlled environment of Montessori would be a tough match for a very social, tactile learner. I student taught one semester in Montessori, and I well remember one young child who was viewed by the staff as a "problem student", when, in fact, he appeared to me to be quite normal - just not their definition of normal.
Since he is quite social, have you considered finding a placement that is less focused in academics? It isn't like he is going to need to catch up for kindergarten, and if he is gifted, he'll do plenty of learning on his own. Just a thought...
