I have thinking about this issue quite a lot recently; Imagine a class of students where students don't ask any questions to teacher; All of the communication is only from teacher to students. ( I myself have attended such classes when I was a student.) In such class why teacher can not be replaced by TV playing pre-recorded video of lecture?. TV can be a big size, high resolution TV giving life like images. In the video, there can a FAQ section thus nullifying the need for students to ask the question. This will bring down the costs of education drastically at the same time giving worlds best education to the masses.