Wow - your son sounds alot like mine! We pulled him from a GA pre-k and have placed him in a private Montessori school due to a very bad experience.
...Ultimately, a severe bite was the icing on the cake at the GA pre-k.
I take it your son bit another kid?
Mr W (25 mos) did this a few times at the homeschool daycare. We talked with him about this. For a few weeks afterwards, when we asked him about school, he would say occasionally, "I bite my friends. I am very bad." We took this as acting out and realized that location was no longer a good fit.
He did it twice when he started Montessori, but has not done it since.
