I don't know what to suggest, but I'm similar to a lot of the people that posted here, in that I always did shitty in school. I just never cared to do homework, but I was always good at taking tests.
The only way that I managed to graduate on time was in high school, I was able to transfer to the county career center. I took electronics, had a lot of great teachers that TRULY CARED, and generally enjoyed myself. It's possible that the school he is in isn't the ideal place for him.
However, the problem he is having needs to be addressed as quickly as possible. I know that my changing schools was only a bandaid for my problem, I've been in three different colleges, with absolutely no direction, and failing classes left and right. OSU kicked me out for my grades. I would hate to see anyone turn out like me, unmotivated and uncaring.