The Mastery-based Learning (MBL) Work Group has examined opportunities to increase student access to relevant and robust mastery-based academic pathways aligned to personal career goals and postsecondary education, and reviewed the role of the High School and Beyond Plan (HSBP) in supporting mastery-based learning. The Work Group members believe that Washington has both an opportunity and an imperative to respond to the dual pandemic of COVID-19 and the structural racism that the school system has never effectively addressed. The collective "why" calls for a transformation of the education system to close both the opportunity gap and resulting achievement gap. This report discusses the barriers to mastery-based learning (MBL) in Washington State and provides recommendations around how to increase capacity for MBL, including the development of a MBL pathway to a high school diploma. [For the interim report, see ED610102. For the summary report, see ED610116.]