Aside: The part about cramming for tests and getting good grades as proof of being smart reminds me of a piece of research (that I can't recall) which found that kids learn more when they are praised for effort rather than praised for being smart. The kids that were praised for being smart tried to maintain appearances by not working too hard (as per the blog post) and subsequently did not improve as fast as the kids who were praised for effort.

On the comment of going from -3 to +3 without falling between +- standard deviations, my guess would be that you'd have to pass through that territory anyway, rather than a spectacular jump from one end to the next, seemingly overnight.