It was a school in rural Mississippi which was next to an Air Force Base and filled primarily w/ children of base personnel --- apparently it was changed away from that shortly after my father retired, I had thought because of legal challenges, but that was from the uncertain organic memory of 10 year old me of half a century ago.
With the wide variety of charter schools which were set up, I'm surprised it wasn't tried --- I would really like to see this educational mechanism revisited and re-tried --- seems like a good fit for remote learning (remote classes are academic and done at ability level, in-person classes are social and done by age level w/ peers.
Yeah, good point, especially at the higher levels. Our public high school offered differential equations as the level after calc only because they randomly had a really exceptionally capable math teacher who was a teacher as a passion project after he'd made his money elsewhere, but most schools don't have access to that sort of capability. Remote learning could offer that sort of headroom in every subject. I guess local colleges sometimes offer that ability.
Maybe some charters do, I'm definitely not an expert.
One of the big regrets in my life is that the tiny rural county school system I graduated from couldn't find a math teacher qualified to teach calculus for my junior or senior year, which precluded applying to pretty much every college I was interested in.