I teach dogs but I have to work with people. So can I chime in?

There are those who feel entitled and it sounds like mom is one of those. If her child is unable to keep up, she is not doing him any favors by pushing him. She needs to get special help for him. He is the one who is suffering along with you and your other 25+ students (who - incidentally - are entitled to an education.)

And the medication thing is over the top.