DS8 has what I would consider a phenomenal memory. He knows almost all of the capital cities, for instance, even though he was never taught and I wasn't aware he was attempting to learn this. But on the WISC (taken at age 6) he was in the average range for working memory. I have a feeling he wouldn't score all that high on the KABC either, but he did very well on the CogAT (esp. on the math and non-verbal sections) and his WISC perceptual reasoning score was 140 something. His computerized math/reading scores which test above level are always in the 98th-99th percentile (he is now in third grade).
He was one of those kids who had a solidly average IQ score at age 3 (just over 100) and then it rose dramatically.
There are so many factors, like the level of motivation, rate of brain development at particular ages, particular disabilities that play a role, etc. He didn't do well on the verbal section on the WISC at age 3 (I think he was actually below 100), probably because of his dyspraxia, combined with a lack of attention to the test, but his CogAT verbal score was around the 92nd percentile.
I think you should consider re-testing on the WISC, and then a general abilities index can be computed if there are gaps between scores.
