So I really had two points: 1. Some ideas (eg proportionality) recur throughout a course of study in mathematics. Pointing out the relationships between these

So I really had two points: 1. Some ideas (eg proportionality) recur throughout a course of study in mathematics. Pointing out the relationships between these ideas is absolutely a useful thing to do, and a student's understanding of these "simple" concepts should mature throughout their study. That's not some profound debatable point. It's just a really stupid simple observation. CC is full of these stupid simple observations that somehow become controversial because of shitty execution. 2. Shitty execution of CC is an indict of our inability to make education an attractive career choice, far more than it is an indict of CC. Having students memorize relationships between angles and points on a unit circle without making sure they can derive those facts themselves is exactly as useless as showing the derivation without giving them any practice at calculating things themselves, for example. But at least CC gets one thing right -- ideas matter. And yes, you also need practice. But rolling back CC (or adopting it) isn't going to solve the fundamental problem with math education in the US, which is that most people who are really good at math don't become math teachers. For obvious reasons. > I'm not getting the proportionality => measure theory link Do you get the link between proportionality and Lebesgue integration? Then the connection back to measure should be obvious. (edit: better example) My point is that proportionality isn't some "stupid simple" concept that CC has somehow over-complicated. It actually does recur as an idea of central importance throughout mathematics, and drawing out those connections is a good use of instructional time. > Second, you forgot to demand... That's a stupid demand. Teaching measure theory in high school as part of a standard curriculum is also stupid. But that doesn't mean that idea of proportionality don't recur, at varying levels of sophistication, throughout a standard age-appropriate course of study. > Except what you'll get is as many opinions on what to spend the 6 years on Right, well, that's kind of the whole point of having a standardized curriculum... Also, empirically, I've literally never seen this happen. Only in the context of after-school or extra-curricular enrichment stuff do people focus on topics they're passionate about, and in those cases it's entirely appropriate.