You are the parent there for you have final choices on what is right for your child until he can take responsibility for his actions. With that said, Yes i would be very upset with seeing a struggling child over come and make progress just to see a teacher take that away as if she/he knows best. Do what works for your child. If that teacher is not letting you participate in your childs education then i might seek a different teacher that wants your child to succeed.
Kids learn at their own pace it might take some kids longer then others but dont rush or force anything he will get it spite all his disabilities he will be fine I took me forever to learn how to tie my own shoes and my husband has had a learning disabilitiy all of his life but he is fine just a few hurdles here and there but no big deal
As a mother, yes you do have a right to be upset. You just want the best for your child no matter what level he may be at. All kids learn differently and at their own pace. My son is 10 and in there 5th grade and reads at a 3rd grade level. Its not that he's stupid because he's far from it. He's very smart. He has a hard time with words and pronouncing them. Also has a hard time remembering what he had read. They fought me the for a year trying to tell me I'm a bad mom for not helping him when that's all I did. I spent hours every night helping him with homework and reading. I told them one day to come on over and be there fly on my wall and watch what I do. And they did.
Its very frustrating when you do everything you can to help your child and have someone put you down like that. Keep faith mama, your lil boy will learn and understand in his own way in his own time. You know him better than they do. Remember that.