It's a fine balance. It's important to stay focused on the curriculum, and teach students how to answer questions that they will encounter in tests, whether in my classes or in future classes. That said, when I get an interested student or group of students, I make every effort to teach subjects from a non-standard point of view. Over the years, I have collected examples that students have found useful, and there is nothing love more than hearing a student pause for a second and say "I never thought of it that way."