Many people often forget what was said in the heat of the moment. They're too much in the 'red' to comprehend what's really going on. Have you asked him why he doesn't want to go to school? If I were you I'd tell him that I'd be marching down to his school myself and talk with everyone there possible, if it helped him get back in class. Most kids don't like their parents comin to the school talking with their teachers, principals, counsellors .. etc. He may willingly go just to prevent you from going yourself. Everyday HE doesn't go, you go instead. Make this a big deal. Hopefully he'll be forced into going in himself.

Maybe not such a good idea but at least it teaches him that you care and it's done in a positive and caring fashion. Find out what's bugging him. Maybe something's happening to him at school.