My apologies, I missed your reply to my post earlier.
We were in areas that had Montessori classrooms which continued post-K into elementary. However, we had decided not to put him in that school here and instead tried a fancy "traditional" private school. Only lasted one year (the first grade year) there. He is at a far better, for him, school since then.
He has not been full-grade accelerated, largely due to his own choice. However, he has been "double subject (math/language arts) accelerated since early on in second grade (eventually, by two years in each subject). He just placed into high school math (basically, a three-year plus acceleration). For him, it's worked well to have age peers (many of them quite bright, it seems) and the more challenging classwork.
Our younger child was accelerated from first to second partway through the year.
