I think it's a question of how to fire up intrinsic motivation. As others said, challenge is a big factor and maybe the grade hop is all that is needed. It also seems like the sort of encapsulated chunking that schools tend towards to spin out grades, etc. are counter-productive for an intrinsically motivated kid with a perfectionist bent. Waging an intrinsic war with extrinsic battles becomes theatre of the absurd.
Without the skip, maybe he could choose an area or two that he is passionate about to explore as far as he wants by relating other topics to it. A shift towards an open-ended learning perspective where there are no limits to how far one can run in a subject may focus the perfectionism away from effort and milestones. Perhaps he could develop his own mind map chart of learning and rate how deep and solid his knowledge is in areas as well as branches for what else he can learn.
