I don't know if I remember the textbooks exactly...but I remeber the things I couldn't do. For example, I remember the high school math teacher (I could tell you her name if need be) pointing at Pascal's Triangle and saying "You might even see a pattern to how the triangle is made."

I didn't see the pattern until years later (in my own defense, the question was asked around 7am, as I was at a "double session" school...at least I was home by 1pm). I can recall a few other things, like hyperbolas...not really understanding how circle formulas worked, struggling to figure out which was the x-axis, and which was the y-axis. I concede, I was something of a late bloomer.

Most US students don't take calculus in high school; I sure didn't. Perhaps 5% do? Something like that, it varies quite a bit by state.