Are all of the other subjects just as not challenging as math? What are his interactions with his age peers like? Is it possible that what he really wants is to rely on a strength (learning math) to provide an escape from uncomfortable social situations?
I think people want to think that lack of challenge and intellectual peers is a problem limited to school, but it continues after school is finished. Acceleration can only help you postpone the problem.
You have a challenging curriculum it's just not listed on the syllabus.
