Have to put a plug in for the Twin Cities area, simply because there are quite a few different options for HG+ kids in several districts, and we have open enrollment here (meaning you can go to school out of district). Our state GT org has a lot of info. On this page, scroll down to find a doc that lists the full-time GT programs.
http://mcgt.net/gifted101Of course, no one place will be perfect for any one kid, and you are unlikely to be able to find a perfect fit school for any PG kid that goes from K-12. That's why I like the areas with several options.
Also, I don't really believe we have the BEST GT in the country - there are so many improvements that could be made. I haven't heard of the best place.