We're outliers in that we told DD her score... however this was because she was convinced by a poor educational environment that she was stupid or that something was wrong with her. I'd say that you share the information with him or others on a need to know basis.
Other people aren't going to be interested in hearing about your results anyway. In the US, it's socially acceptable to brag about athletic or artistic achievement, but not intellectual. Your biggest challenge will probably be keeping him from being bored and getting him the most appropriate education (thought if the school brought it up to begin with, that's a good sign).
The key thing in understanding behavior is to realize that some of the intensity and sensitivity is due giftedness and not an attempt to misbehave. That can be helpful to you as a parent. Otherwise you just keep loving them and accepting them as they are, you know?
Oh, and you stay here so that you can commiserate and brag in a supportive environment.
