Every kid, and every family is different though, and the wonderful news is that there are usually many ways to 'course adjust' as we get to know our children better.
I have not observed much flexibility in the school system. Few MA public schools have gifted programs or guidelines for whole grade or subject acceleration, so I don't see many alternatives to starting gifted children in KG early. Typically one needs to keep them in a private school through grade 1 before transitioning to public school.
