[ndeine]

That's my perspective on it. I first took calculus as a junior in high school, and the majority of it boiled down to memorizing what the derivative of `x` type of function is and what the integral of `y` type of function is.

When the AP test rolled around I was really struck. The problems were about the flow rate of water descending into a tank and what happens when you put a drain here with this rate of flow, etc. Completely different from our earlier problems which could be solved by rote memorization. And from my perspective - one of a student who knew a bunch of calculus "rules" but lacked understanding of how calculus really worked - this was incredibly difficult.

I got a 3, which is passing, but opted to take beginner-level engineer's calculus when I got to college anyway. Even if you "learn" calculus in high school, it does not teach the level of mathematical maturity required to understand the higher level manipulations. This kind of thought is the foundation for any good engineer, and I have no regrets about retaking the course.