Both the New York Times and the Washington Post spilled ink over the phenomenon. Several authors resorted to old-fashioned books to discuss flipping, including the two teachers who allegedly originated the technique (see Flip Your Classroom: Reach Every Student in Every Class Every Day by Jonathan Bergmann and Aaron Sims). None of that tells us anything about the number of teachers who actually flipped their classrooms. No one has offered any firm measure of the practice or, more importantly, assessed its impact on student learning. In case you missed all the hype, the flipped classroom is a form of blended learning in which students learn online at least part of the time while attending a brick-and-mortar school. Either at home or during a homework period at school, students view lessons and lectures online. Time in the classroom, previously reserved for teacher instruction, is spent on what we used to call homework, with teacher assistance as needed. How can this improve student learning? Homework and lecture time have merely been switched. Students still learn through a lecture. And many online lectures are primitive videos.