My son will not attend special education classes what can I do about this?

He started doing this during his freshman year. He skips every special education class he has. He says he hates it in this class and he only wants to attend main stream classes. He refuses to go to the classes or go to his meetings. Grounding him doesn’t work and he is 15 years old. He says that it’s embarrassing and that he feels humiliated. He is covering his disability so that nobody knows. And that when he goes to the class he just wants to harm himself because he won’t accept going to this class. But he does accept his learning disability but won’t tell anybody about it. He just keeps telling me and his mother to please don’t make me go to that class room. Or the meetings, that being in the room or getting extra help makes him depressed and feel worthless. But when he has nothing to do with it he feels no stress or depression but feels normal. He says that he rather die than to go to this class room and that he is not mentally retarded. He is mostly in main stream classes