That's wonderful!!
I'm not sure if you have read about extended norms and GAI calculations for the WISC IV on this forum. But since the psychologist has never tested anyone that high, he/she may not be aware of them.

Here is the link for the extended norms for the WISC IV.
http://www.pearsonassessments.com/N...C-8E4A114F7E1F/0/WISCIV_TechReport_7.pdf

Your son may have earned more than the max 19 scaled points for a particular subset (looking at his scores in Perceptual would be a good bet) and this report explains how to count beyond 19. You may want to bring this up with the pschologist and ask to look if he earned more than a 19 and have it recalculated using the extended norms. Not too many psychologist have experience or know about it because most of them do not test kids at the upper limits of the test.

GAI may be useful as well as the score takes into account the Perceptual and Verbal.
Here is the link for it: http://www.pearsonassessments.com/N...DA-05888C7CC082/0/80720_WISCIV_Hr_r4.pdf

That would be my advise to get the best picture you can from the WISC IV for your DS. There are other here who know a lot more than I do, but when we retested DS7 it helped get a better picture having the extended norms and GAI calculated.