What if all students had an opportunity to work through content at their own pace? What if all students had to master content before they moved on? The authors take their flipped-classroom model to the next level by flipping their classroom for mastery. In the flipped-mastery model, the teacher begins by organizing content around specific objectives, giving students a menu of options they can use to master those objectives. To ensure that all students--even those who have trouble keeping up with the content--understand key concepts before they move on, the authors "front load" the essential objectives for each grading period, saving the "nice to know" objectives for the end of the grading period. Assessments consist of formative checks and summative retakes. The authors note that the most important part of their assessment system was "simple conversations we had with our students."