Thanks so much for all the great advice!
I know that both schools have gifted programs, but I don't yet know what all that entails. I also know that one of the schools allowed early entrance to a child in the recent past, after she jumped through several hoops for them. (This is a big reason the school is on our list -- that and the fact that she and her family felt she had a good experience in the school.)
master of none: I really appreciate the suggestion to ask hypothetical questions, speak of our son's love of astronomy, and generally try to stay low key. Thanks also for the links to previous discussions. I will look through them.
amy: Good to know that mentioning early reading may be better received than other information.
Peter: I would love to keep my son home another year -- or two, or indefinitely. We are also looking into homeschooling, but I don't know whether we can make it work, logistically.
polarbear: You're absolutely right, things can and do change. However, we are in a huge metropolitan area with many areas we would be happy living in, so using schools as a deciding factor works for us, for now.
The area we're currently in has solid middle schools and a well-regarded high school. But in addition to looking at the two public schools, we're also going to look at some private schools (which I don't know we can afford) and public schools in another district.
Thanks again for all the great thoughts!
