The Common Core Standards for Mathematical Practice (CCSSI 2010) and NCTM's "Focus in High School Mathematics: Reasoning and Sense Making" (2009) present a vision of high school classrooms in which the majority of the activity involves students working on rich mathematical problems and engaging in mathematical discourse. This model stands in sharp contrast to lectures, demonstrations, and independent practice that have dominated classrooms in the United States (Stigler and Hiebert 1999). In the quest to spend more class time doing meaningful mathematics, teachers have increasingly turned to technology to support student learning. One recent model is the flipped classroom. This article describes the history of the flipped classroom and reports the results of experiments with variations on the flipped model with the authors' own secondary school mathematics students. A bibliography is included.