It's at the other end of the college curriculum, but I had a somewhat similar experience. I arrived at college having passed AP Calculus but without having taken any trigonometry. After a couple of semesters I realized I really needed to address my lack of trig knowledge, so I enrolled in a course. The prof who was teaching it recognized my name and asked me to come talk to her. She suggested that I drop the course and instead spend the semester grading papers for the class, rather than taking it.
I did as she suggested, and I think I learned more trigonometry than any of the students in the class.