Watching this thread as Boston is a possibility for us as well. I suspect we are dealing with more optimally gifted rather than PG so a strong public school would be adequate--Newton I think would be my first choice but I don't think we could afford it.
Several suburbs of Boston have public school that look good on paper, based on the fraction of students going to 4-year colleges, average SAT and AP test scores, etc. Besides the favorable demographics (a largely White/Asian, affluent, college-educated population), some of the success may be due to programs parents are paying for outside the public schools. A large fraction of parents we know are sending their children to places like the Russian School of Math
http://www.russianschool.com/ (started in Newton, and now expanded to other towns) or the Math Club
http://www.themathclub.com/ in Lexington. Many Chinese parents send their children to Chinese school one or more days a week, and these schools are not entirely focused on Chinese culture. It may be better for some families to live in less expensive towns within driving distance of these towns, so that they have money for extras such as these.
