Well, you might want to cross-check the list of high schools offering classes beyond calculus with those that have multiple kids making USA(J)MO before writing off kids that take those classes as having gone through a bunch of fluff courses. IIRC, there are a couple high schools that have more than one kid at that level - I doubt that those kids are weak in problem-solving and proofs! I think it is quite possible that both of the following are true concurrently: (a)there are many kids getting through HS math courses that are weak and (b) there are schools that have kids who need college level math prior to graduation from HS.
My district is very proud and stubborn that THEIR honors math classes are the most rigorous classes around. I'm not completely convinced but I am not unhappy with their rigor either. My son's been struggling to get good grades, I've heard the teacher uses problems out of AoPS on her tests. My son's High school has multiple kids who get top scores in the country in USA(J)MO, although I'm not sure if that isn't more because of all the outside tutoring these kids have been in for years than the districts curriculum.
I am still confused as to what the kid who is a freshman and in my sons Algebra II class and taking today's AP BC Calculus test is planning. I don't believe our H.S. will give the kid credit for the course. Perhaps he plans to enroll is math courses at university? I expect he wanted to skip to Calc this year but the school wouldn't let him? Years ago my husband took maths classes at university starting in 9th grade, and I know it can be done. But most of the kids who finish Calculus early around here, just don't take math for a year or two.
