This is the same reason people don't take calculus in ninth grade, or organic chemistry in tenth. "What will you do if you run out of classes?" I don't know, learn on your own? And once you run out of learning, do your own reseach? You cannot simultaneously view school as a place to advance your child's learning, and also a place you need to hold off on their learning for. Pick one, and if you pick the latter, admit to yourself that they're not going to school, they're getting babysat.
I actually attended a school system which had a system in place for that --- see my post elsethread.
Unfortunately, the Mississippi State Supreme Court ruled it to be an unfair and illegal educational system which conferred undue benefits to the students able to take advantage of it and that the lack of a commensurate compensation for students who were unable to do so was manifestly inappropriate.
I can get the latter one, which is why I think we shouldn't just have magnet schools, we should have free, government-run magnet boarding schools. Or, alternatively, how much would it really cost to provide a chauffeur service to kids who have demonstrated intelligence and need? If schools can provide personal aides to 1% of their population, I'm sure they have the budget to treat another 1% equitably.
The crux of the lawsuit as I understood it from hearing about it from letters my parents received from involved parents was that a student who was unable to learn at the accelerated pace and graduated with only a high-school diploma sued to either be allowed to continue to attend the school for 4 additional years, or to be granted funds to attend a college.
The school was the only public school in the county, and was attended by all the local residents (the student who initiated the lawsuit was one of them) and the children of the personnel of the local Air Force Base --- it was the matching DoD funding which made the school system possible.
From what you say it sounds a boneheaded decision, to deprive students from a good education because other students aren't ready for it.
The UK excels at something similar, where they are trying to undermine private schools and even higher level public grammar schools. This is because it's only privileged children who can afford to go to there, and the outcomes are way better then public schools.
There is a term for this: "the politics of envy",
where it's better to funnel everyone through the same mediocre system so that nobody can gain an advantage. This was very much the logic behind the recent law to tax private schools, and it's an idiotic principle.
