kids in bad neighborhood. Enhance his friendship with his friends who have good study habit, socialize with the parents and green lights for playdates....
Don't set goals too high, tackle one problem at a time. I would tell him to get min. 80% of everything(homework, test, projet etc..) is his duty and responsility as a student. Any performance better than that will get reward, below punishment.
Support in every possible way, but don't do works for him.