There are research articles saying HG/PG kids brains develop differently than ND kids. Evidently ND kids reach maturity (full thickness) of cortex at about age 7-8, whereas HG/PG continue to develop until age 11. Although I'm probably butchering the findings and am too lazy to look it up right now, what this has meant to me is that our kids have a bigger window of discovery that is important to nurture. Their IQs can indeed change during this period. DS's best friend had an IQ jump of 15 points from age 7-8 to 10.
My DS 6 is 4th child and I have not worked with him much (old, tired face). But I do see that his processing speed improves as he gets older. His teacher plays "around the world" where she holds up a math problem and the one who solves it first wins and can keep winning if no one solves subsequent problems faster. This has helped him with math facts, but I don't know how to do it in HS setting. Having a classmate who is advanced encourages him to advance. They are working out of Comprehensive Curriculum books, some ALEKS, and now a 4th grade Houghton-Mifflin Math book.
