I teach High School math and have been flipping for 4 years. In my typical manner I bit off more than I could chew and switched to mastery early on in flipping. It was a lot of work but I saw some amazing learning and engagement from my students. I have backed of a little bit from master at this point since I am at a new school and teaching new content therefor making videos again. I now teach in more of a semi-mastery style in which I use mastery checks along the way but still have some firm due dates. I am still searching for the right balance that will keep my students learning and motivated while also making class engaging and challenging.