We had a great experience with an arts-based preschool. It did not have an academic curriculum, but did have a strong emphasis on music and art, and also on child-led group projects (like putting on a play based on a personal story their teacher had shared). The fact that my 2.5 year old dd was reading at a 1st/2nd grade level already was a non-issue.
We kept dd and her twin brother there until starting K in public school at 5 yo, the specified age for the district. They are now 12yo and in 6th grade, both engaged and happy and very high achievers.
