There's a lot variances with the public school systems and with gifted kids. There are tons of factors involved - the school system, teachers, curriculum, other students, child's social/emotional maturity and toleration level, rate of acceleration, etc. I used to teach in a public high school in MA years ago so I've also seen in it from the inside as well as from the outside.
My eg/pg 2e DS was in a pre-k, public special needs program in NYC and MA before we withdrew him and put him in a private gifted school because he was 4.5 yrs old and writing 4-letter words, such as ramp, and reading and bouncing off the walls from boredom. Moreover public school in MA wanted to keep him in special needs for kindy due to attentional issues (without a diagnosis) which would have been a major disaster.
At private gifted school #1, DS whizzed through the pre-k/k/1st grade curriculum within 2 1/2 months and we were then told the school could no longer accommodate or would accelerate him. At the time, the headmaster said DS was socially/emotionally too young to be put in the 2nd/3rd grade class. This school was structured and there was less leeway with making accommodations so we brought him to private gifted school #2 which was considerably less structured and more Montessori-like. Private gifted school #2 lasted just over a year.
I'm now homeschooling/unschooling DS - which has its advantages and disadvantages like formal edu in private or public. I'm able to accelerate DS and work with his pace. I'm loosely following a general curriculum guide, which a 2e expert advised me to do, but DS can do 3rd and 4th grade work or more being at home, which he wouldn't be able to do at the public schools. One grade skip maybe, but two grade skips or multiple grade skips are out of the question in my district.
I will say that I took my son to a 2e expert this summer. She said it's public, private, or homeschooling. She said we wouldn't get much from the public schools - which I already knew based on our discussions with school dept after the test results (FYI - parents are legally entitled to testing through the public schools but you must put the request in writing).
