What academic areas are his weakest and his strongest? Did you have any other testing done at the same time as the IQ testing - achievement testing or other? If he had achievement testing, how did he do compared to (either grade or age), and were his results relatively similar across subjects or were there relative highs and lows? Were there highs and lows on the subtests of his IQ test? If you *don't* have the subtest scores, it might be very useful to see them.
High IQ kids don't always look like what we tend to think of as high IQ - the world often expects high IQ kids to be extremely driven, exceptionally organized, and to do very very well in school. In reality I think that it's usually the kids who are motivated and driven that do well in school, regardless of IQ. That motivation to succeed is something that seems to click in a bit later in schooling though - so I wouldn't expect to see it yet at your DS' age. What I also wouldn't expect is that achievement would fall well below ability in the early years of elementary school - even if there's not any signficant differerentiation happening. A gap between achievement and ability *might* indicate the presence of a learning challenge - also the note that your ds needs extra help in certain areas points to a potential challenge.
Best wishes,
polarbear
