Google search!
My ds6 is in first grade at a private gifted school; he was at public school for K and it was not good.
Every gifted school is different; some work up one grade across the board, some are really good at differentiation and others not so much, some do great with highly gifted+ kids and some don't. Just like any school, they all have strengths and weaknesses.
At ds6's school, there is a 125+ IQ requirement. Kids are in two-grade homerooms (first/second, third/fourth ...); they do social studies, science, art, music, etc., with that group. Math and language arts are in the same time slot for all grade, and kids are grouped by ability across grades for those core subjects. This allows a lot of flexibility for the HG+ child.
In addition, they offer a lot of fun afterschool extras; ds6 is taking an astronomy class, a watercolor class and doing Destination Imagination after school, all his choice. The upper grades have academic teams for state and national competitions.
So far, ds6 loves it. He's meeting kids that are much more like him, and being smart isn't looked down on but celebrated at this school. The downside is that it's really expensive, and that cuts down on at home extras like vacations.
We're lucky enough to live in a large urban area with a few gifted schools. Depending on where you live, there may be several or there may be none! Do an Internet search and see what turns up.
