By Salman Khan, Time
Each school day, millions of students move in unison from classroom to classroom where they listen to 50- to 90-minute lectures. Despite there being anywhere from 20 to 300 humans in the room, there is little actual interaction. This model of education is so commonplace that we have accepted it as a given. For centuries, it has been the most economical way to “educate” a large number of students. Today, however, we know about the limitations of the class lecture, so why does it remain the most common format?
http://ideas.time.com/2012/10/02/why-lectures-are-ineffective/