My dd9 was also tested twice on the WISC with scores that didn't have an overlap btwn confidence intervals. At 7.5, her GAI was 147, I believe, and at 8.5 it was 127. If I'm off, it's by a point on either one (scores aren't at hand).
In our instance, I'm not sure that she is really a 147 kid, but I think that she is more than a 127 kid. Her second testing came at the end of a year in which her 3rd grade teacher spent the entire year telling her that she was just a good guesser and really squashing her self image. She also had the pattern Dottie mentioned of missing easy questions early on that pulled down the totals. I'd guess that she falls somewhere in between the two, but time will tell.
If your son had anxiety issues, self image doubts, or any of the other stuff that was going on with my kiddo I could see those impacting him similarly to how it did her.
