the word on the street is that the knowledge section is notorious for scoring low in younger GT kids. It could be that is what he is basing the statement on (if indeed knowledge is lower). Knowledge reflects what has actually been learned...or at least exposed, and if you have a really smart kid that hasn't necessarily been in a school like atmosphere, that might be lower, and it would drag down all three of the scores you were given.
Dottie,
That's the case for myDS9. Knowledge was the lowest index(123) on his SB-5. He was 8.7 years old, so he wasn't really "younger" though... I was also puzzled by the huge difference between verbal(18) and nonverbal(10) knowledge. He is 2e, but still......Do you know which subtest on the WISC-IV is equivalent/similar in measuring nonverbal knowledge skill?