The state of Washington, through the Mastery-based Learning work group, is embarking on an exciting journey to reimagine the state's education system. The work group believes that mastery-based learning (MBL) is a way to transform the education system--with this approach, teaching methods are designed to equitably engage each and every student in ways that best support the individual student's learning journey. Through work group members' own experiences with MBL in Washington and across the world, and after hearing from Washington students regarding their experience with MBL, the collective "why" calls for a transformation from a traditional system to an MBL approach because this enables: (1) A focus on meeting the needs of each individual student; (2) Students to enjoy relevancy, engagement, and choice in their learning; (3) Freedom to actively embrace inclusivity--compassion and belonging for students; (4) A culture of celebrating the learning and innovation that comes from failure and values knowledge and skills that students already have; (5) Each student's learning progresses at their own pace; and (6) A way to get rid of labels and create a system that recognizes that each student's learning happens differently for each subject. This report provides the work group's vision for mastery-based learning in the state, activities of the work group this year, preliminary findings, and areas for further exploration during 2020. For context, the report also has appendices on definition of terms and the state of mastery-based learning (MBL) in Washington as well as national and international examples. [For the full report, see ED610100. For the summary report, see ED610116.]