Get him a copy of a tabletop role-playing game, a notebook for writing down campaign ideas, a couple of people willing to include him in their group as a part-time DM, and (importantly) an understanding from the teacher that when he is sufficiently done with the classwork, his time is his so long as he isn't disrupting other students.

Have him learn Go. It's not only a game; it forces you to examine your thinking patterns, review your expectations, and meta-model other people's model of your mind. It's a tremendous booster.