We divided our high school physics teaching experience into three groups: first year teaching physics, second or third year teaching physics, and four or more years of experience teaching physics. We did this because everything is new for teachers teaching a course for the first time. The second and third time through the course, teachers learn from past experiences and hone their approaches. By the time a teacher is in the fourth year of teaching a course, he or she is more comfortable with the material and better able to understand the ways in which different approaches work with different topics.