I self-taught myself trig and calculus in high school. I wasn't told about AP classes until it was too late to sign up and then I was told it was a waste of time to take the test without the class. I signed up for the AP test anyway, spent a semester self teaching and got a perfect 5 on the test. It took some dedication but really it wasn't that hard to learn. Later I found out that none of the students in the class got a 5, mostly 3s and 4s.
I got a 5 as well, but in my case it was less a function of calculus mastery and more a function of knowing how to program everything they asked for into a TI-89.
(I've since gone through a few calculus textbooks to actually learn everything that gizmo let me fake an understanding of.)
