There's a teacher at my school who teaches nothing but Geometry and Statistics. He's a WONDERFUL teacher...the kids love him. His honors geometry class is one of the most challenging courses I've seen in high school. He's maybe 50-55 yrs old. I was talking to him and a few other teachers a few days ago and we were discussing a problem. It involved basic integrals, which is a Calc 1 topic. This teacher said something like "I totally forget how to do integrals. What are they again?" My school offers up to Multivariable Calculus (which I could never teach), but I really want to keep up with material up to Calc 1 or 2 at least. I just got out of college 2 years ago, so everything is still really fresh in my mind. But what do you do to make sure that the content above what you teach doesn't go away? Like how does a World History teacher remember European History well enough to teach it, etc.?