I believe your son is in a program that is not doing him any good. In my opinion, the teachers did not handle the original conflict well and it resulted in a child getting physically hurt and your son (and the other child) getting no guidance to how to manage a conflict better next time. The whole point of this environment is to develop social/emotional skills, right? Or what? What is he there for? If you want him to develop social/emotional skills, one of those (a big one) is conflict resolution and communication. The following links may be helpful to you and are methods that a good teacher should be using (in my opinion). Might I ask what education or experience the teacher has, that was there during the conflict? No, it may not mean everything, but it sounds like she can't safely manage a classroom or teach social/emotional skills.
http://www.janetlansbury.com/2010/04...-9-guidelines/
http://www.naeyc.org/files/yc/file/2...uidanceBTJ.pdf