One of the most rigidly common core-based math curriculums was the New York State math modules, which we used in our school for ten years. It didn't move the needle on math achievement on state math test scores. Now, full confession here: I am NOT a "math guy." I can calculate tips in my head, add and subtract mentally, know when to apply these basic operations to a given situation, multiply, divide, etc. I don't get advanced algebra, geometry, calc, trig or any of that other stuff. It makes no sense to me. That all said, I found the teaching of the common core method of math highly confusing for some kids. It's intellectually fascinating to know what is truly happening when one divides fractions (fifth grade CCSS). However, writing about it is extremely frustrating, and there is a lot of writing about math in CCSS math classes. At least the ones that use modules like ours. Now I DID learn some nifty new ways to solve problems, I will admit, and I enjoyed teaching some of those ways to my students. However, I knew the "standard way" anyways, so I didn't really learn anything new or useful. I suppose my over-all experience after ten years of CCSS is "meh"... some good, some not so good, some that needed a lot of revision.

On another note, I agree with your definition of a standard as something that is expected to be learned by the end of a school year. However, I think most schools and teachers in general interpret it differently: as something to be taught by the end of the school year, but not necessarily to any sort of mastery. Quite different. Until we've settled THAT little argument, American schools will always be good, bad and ugly, IMO. In any case, good article.