How are expert educators using games in their classrooms to give students agency, while also teaching twenty-first century skills, like empathy, systems thinking, and design thinking? This question has motivated Matthew Farbers Game-Based Learning in Action: How an Expert Affinity Group Teaches With Games showcasing how one affinity group of K12 educatorsknown as "The Tribe"teaches with games. They are transformational leaders outside the classroom, in communities of practice. They mentor and lead newcomers to game-based learning, as well as advise game developers, academics, and policymakers. Teachers in "The Tribe" do not teach in isolationthey share, support, and mentor each other in a community of practice. Farber shares his findings about the social practices of these educators. Game-Based Learning in Action details how the classrooms of expert game-based learning teachers function, from how they rollout games to how they assess learning outcomes. There are plenty of lessons to be learned from the best practices of expert educators. These teachers use games to provide a shared meaningful experience for students. Games are often the focal point of instruction. Featuring a foreword from James Paul Gee (Mary Lou Fulton Presidential Professor of Literacy Studies, and Regents Professor), this book comments on promises and challenges of game-based learning in twenty-first century classrooms. If you are looking to innovate your classroom with playful and gameful learning practices, then Game-Based Learning in Action is for you!