The answer to the question is: the once-innovative practice remains popular in the rhetoric of instructional reform in both university and K-12 classrooms but it is devilishly hard to pin down exactly how many professors and public high school teachers have adopted and used the practice regularly in their lessons. Many U.S. high school teachers and professors—how many I do not know–say that they have “flipped” their class lessons but what such classrooms look like in practice is anybody’s guess.

A Wikipedia definition of “flipped” classrooms captures the gist of the innovation in both public school and university classrooms:

A flipped classroom is an instructional strategy and a type of blended learning, which aims to increase student engagement and learning by having pupils complete readings at home and work on live problem-solving during class time. This pedagogical style moves activities, including those that may have traditionally been considered homework…