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DS teacher is concerned about his social skills because the other kids have no frame of reference for what he talks about, her words not mine. She is more concerned about this than I am because I don't think he is miserable and I don't want to send the message that he needs to change himself to fit in.

That's not his social skills, that's his intelligence! You can't expect a 4yo to know how to tailor his conversation to his audience. At least he's talking to them!