There were differences in the teachers' knowledge of physics and their teaching experience. The student populations at each school varied as well. For example, School A was a small suburban high school with an experienced physics teacher and an affluent, high-achieving student pop-ulation. School B was a rural high school at which the teacher was teaching physics (out-of-field) for only the second time, and the student population was primarily low income. School C is a high school in a small city with a diverse student body at which the teacher has a strong back-ground in physics but typically teaches math classes.