I graduated college with an Electrical Engineering degree, so I said I knew calculus better than most other people. They then asked me to teach them some calculus. I turned to the board and prepared to write down some formulas, and then they threw a wrench into the works. They said they knew how to "plus and minus" and nothing else. I said I couldn't teach them calculus then, because they needed more foundation first. This was a test to see if I could bring myself down to the level of the person I'm teaching, and if I could switch tracks quickly.