DS knows his SAT & SCAT scores and we've discussed those at length. He understands that he scored quite well on the IQ test and he knows that the score led directly to him skipping another grade level.
We opted not to tell him his IQ as the score all by its lonesome does not provide enough meaning. There's an awful lot that goes into that score, and in our world, the individual subtests turned out to be more meaningful. Additionally, the WJIII Achievement test results were just too plain scary to divulge.
He's only asked once, and it was part of a larger discussion. He was (or at least seemed) totally fine with not knowing. He actually got within a point or so one year when the kids at CTY were toying with calculations while discussing the old age-based representation. Funny.
-- -- --
We've had regular discussions about DS's brainpower, smarts, intellect, whatever you want to call it. And these discussions are extremely important as a means of helping him maintain a balanced perspective of his own abilities. We explore his various strengths as well as his weak points. And quite frankly, his score wouldn't do diddly for enhancing his understanding. (It certainly wouldn't help him remember to put his name on his papers.) For our son, knowing The Number would only serve to distract.