It is important to set age-appropriate expectations. My parents always did. I feel this is a time and place matter.

Can he try tucking on his shirt, or playing with a pencil or his collar. My son is going to be 13 and he broke his habit of soaking shirt by constantly biting on it when he is stress by doing the other 3 things. He change this 3 years ago, he said he was getting older and need to fit in.

My older daughter non autistic sucked her thumb till she was nine my ex broke her it was her security because of severe anxiety if I had to do it again I would try to only make it for private times instead of stopping it all together it had a terrible affect on her. Do what your heart tells you not society