I'm glad your teacher supported you towards actual learning. My teachers supported me, too, as well as they knew how: I got to work from a Year 7 textbook for a few weeks in Year 5, and I got handed a curriculum-restricted calculus textbook when I kept asking why we had to memorise the constant-acceleration equations of motion. Whenever I asked for more, I consistently got told to wait until the next stage of education.
We had one lesson where we were given an open-ended problem from outside the curriculum – about balls bouncing around snooker tables – and asked to solve it. This was something I'd worked on before, and while I didn't quite have enough time to write down everything I could, I did get far enough that I got in trouble for being incomprehensible. (They could follow the beginning bit, but then the reading order instructions got too hard to parse. Don't know why: I made sure none of the arrow-lines were parallel for more than half the page, so you could follow them fairly easily with your eyes.)
Now let's make our anecdotes fight to the death.
As for why I generalise across "all Western nations": it's because the problem I describe is present in all the countries I listed, and while I have no information about the others, my theoretical model (incentives due to curriculums and exams) says it's probably present everywhere in this education system that's near-universal amongst… sigh… "Western" countries.
" the library having no books on maths outside the curriculum, " Where I grow up there have been university books for math and physic at the local library which I read.
" getting marked down for using concepts from outside the curriculum in schoolwork… " Many universities in Germany offer courses for high schoolers and I was supported by my teacher to visit them. Also I could present "a proof" ih high school why the e - function's derivate is the e-function. Or an introduction into particle physics.
This is only one datapoint but much more than the zeros proof of this thread. My gut feeling of HN says its again American to extrapolate their home grown problems to other parts of the world.