This page lists some programs:
http://www.massgifted.org/education
Brockton, MA also has a well-established substantially-separate program from 4th grade up, which is not listed on this page, for some reason.
http://www.brocktonpublicschools.com/page.cfm?p=26 It originated as a 98%ile program, but now edges closer to 90%ile.

I've just glanced at the first few towns on the MAGE list.

It looks like Arlington currently is running a 90th %ile enrichment program.

Bedford's homepage suggests that they are looking for 98%ile kids. Who knows how that looks IRL.

Beverly and Brookline do not have G&T programs. I did my training in Brookline many years ago, and I would echo Bostonian's comment that the self-perception is that those inner 'burbs are so fabulous that all their children are "gifted."

...pronounced like the long vowel and first letter of the alphabet...