I'm in the Boston area with a 2e/pg ds8. My son has attended two of the private gifted schools on Hoagie's -
http://www.hoagiesgifted.org/schools.htm. He's now being un/homeschooled because neither school could accommodate him in terms of acceleration and there's really nothing else around. I spoke to Acera but they were newish (less than 5 years old) and would not have worked out.
Hoagie's does list US and international schools that you might consider. Please bear in mind, that with any of these schools, it really depends on the teachers, curriculum, ability to accelerate/accommodate, LOG, other students, etc. on whether your child will find a match. There's a lot of variables with schools and lot is going to depend how much your child will or will not tolerate in a particular school environment. Unfortunately, you don't always know how your child is going to react until they're placed in a particular school environment.
Many of the private gifted schools will accommodate a few grade skips or maybe more in one subject, but IF you've got a child working 4+ grades ahead across many subjects you may be out of luck. Some kids are fine being in a public/private school setting with modest accommodations. Others are not.
My advice would be to look at alternative schooling options online and all your options (even crazy ones) before ruling them out. There's a lot of free/open source un/homeschooling opportunities today that might work for the academics. Khan, BBC, Open U, and many, many others would offer both the flexibility and acceleration opportunities. There's also a number of virtual schools online (many fee-paying) which you might want to consider too before ruling them out.
Also, the situation can change very quickly with pg kids. One minute, they may be doing addition and the next minute they're doing algebra or calculus. Nothing is etched in stone here.
