But a number without context is pretty meaningless, so until he is ready to understand the context...no numbers.
Yup! We have a couple "things" about sharing numbers in our house. This is the first one. Until DS knows exactly what the test does and doesn't measure, and understands the statistics, he doesn't get a number. And actually we've never discussed the testing in terms of IQ -- he probably has an inkling that it's known, but it's not on the table if you know what I mean. It is, however, in an unlocked file cabinet with all his other school-related records, so if he were to dig it out he could see it. (And actually he has the statistics pretty well down pat now too...)
Second, I don't share The Number with people in general because people in general
don't understand the context. They don't understand what is and isn't measured and they seriously don't understand the statistics. I don't mind that they know he's in DYS -- which is really enough of a hint to get a good estimate anyway -- and I've said enough here and there that someone who knew what they were doing could probably piece together enough to guess it within maybe 5 points. So that serves as a "gatekeeper"... LOL Anyone who knows enough that I'd let them know numbers can probably figure out the numbers on their own.

The third thing is that we live in a very VERY small town. Nothing is secret (for long anyway) and while that has its benefits, it also means that if I were to let anything slip it would a) get around faster than you can believe and b) enter the realm of Topics Of Discussion. Especially in small towns or close-knit communities, everything you offer gets to be handed around...
with commentary. It's like something that came up on the thread about media attention -- you really are putting your kid out there to be talked about. So even if I thought I could tell one person, it would quickly get around to the handful of people that I really wouldn't want to discuss it with. I'm sure enough people know enough that there's some speculation around town, but speculation is miles apart from the authoritative quoting of Data.
And the last thing is, The Number really doesn't matter as much as what he does. If he's achieving at a solidly high level (and he is), everyone can see that. They don't need a number to prove that he's really doing it. If he isn't, then the number isn't getting him very far. It might be different if he had a lot of scatter, or if there were 2E issues where people needed to know how to accomodate him, but as it is he's well represented by his achievement, and that's a bit easier to share with the general public.