Swap Lectures with Homework

I have always liked the following idea for education. Ask students to watch a lecture on some topic at home, and then do the homework with the teacher in class. The United States has an enormous number of teachers, but only a small fraction of them are truly fantastic lecturers. So why should every teacher give essentially the same lecture? Why not record the best lectures, put them online, and assign them as homework? Then class time could be used for what is much harder to do alone: solving problems, asking questions, discussing mistakes, and getting individual help from the teacher. There are obvious advantages. A recorded lecture can be given by someone who explains the subject exceptionally well. Students can pause the video, replay a difficult part, slow it down, or go back to something they missed. A live lecture marches forward at one speed, whether or not everyone is ready. There is also an advantage for teachers. Giving the same lecture every year or every other year might…