One thing I can suggest is really digging into all the available schooling options in your area. Maybe you have and, if so, I apologize, but sometimes schools outside the normal scope of "public neighborhood" or "expensive private" seem to just fly under the radar.
I'm thinking of organized homeschool co-op schools, smaller private schools, magnet schools, religious schools, and parent-driven "custom schools." The appropriateness of a school for a gifted child is often a function of the particular staff and attitude of that specific school rather than the type, style, size, or philosophy. That means you have to check them out personally and individually.
Here in the PNW, there's a whole quiet underground of alternative education options that operate by word of mouth. Even some of our public magnet schools are specifically barred by the district from advertising their existence.
