Thank you all for your kind reply.

I will still do the ADOS test to get my mind set next week. So in the future, I can show people the result instead of trying to protest my boy.

Also I am looking for a preschool who can be just for 3 years old. Montessori may not fit him now. Or maybe just this teacher does not fit him any more.

Hopefully he can step out of this stage soon. His father is similar when he was a kid. He was a late talker too and kind of shy. But he is totally fine now.

Thanks again for all your help. It makes me feel much better.