Any education is good. My brother can do addition and subtraction. He an also write and read children's books. Do anything you can for him. He may be delayed in more obvious areas, but there are also areas where these children are ahead. Help him find those.

Yes, having a non verbal child doesn’t mean they can’t/or don’t know anything. Still work on all skills with them, because they are capable, they have a brain. Think Helen Keller, she was deaf and blind, yet, look what she was able to accomplish.