I have nothing very helpful to offer, but just wanted to send my best wishes. Don't forget that some true geniuses did not speak until very late (not exactly your situation, but related), just because they weren't ready. My best advice would be to find a helpful expert, like a psychologist whom you love, and rely on their testing and advice. It might take several tries to find the right person, but that one right person could make a world of difference with advice. It also sounds like the teacher is at a loss, this is outside of her scope (been there, done that with my two kids and their teachers) and she needs guidance. Once you have a clear vision of where you are, you can guide the teachers, too.
