A few years ago, a friend of mine was in very same situation. They took their kid out of private school and moved to a medium range public school where the kid was ranked in the top group.
That dude got into Duke.
Private high schools are great if your kid is at the top. But top colleges tend to spread their admissions across schools. Better chance if you are at the top of a reasonably good school.
Cut the bad wounds to heal better. This, will take a strong mind to make such a hard decision. Are you ready? Are you capable? Are you willing to?
(These were the questions my friend asked himself a few years ago)
