The Mastery-Based Learning Collaborative (MBLC) is a demonstration project taking place in 24 schools in Washington State. The schools receive funding and participate in professional learning and a statewide network to support implementation of mastery-based learning (MBL) and culturally responsive-sustaining education (CRSE). The initiative's overarching goal is "to inform future policy by helping decision makers better understand what quality mastery-based learning looks like, how long it takes to implement, and what resources are necessary." The Washington State Board of Education (SBE) is leading the MBLC, with executive sponsorship from SBE, the Office of Superintendent of Public Instruction (OSPI), and the Professional Educator Standards Board (PESB). The Aurora Institute is evaluating the initiative to identify effective policies, practices, and system changes that can support MBL implementation throughout Washington's K-12 education system. This report presents evaluation activities and findings at the end of Year 2 of the initiative, with a focus on establishing a baseline for understanding changes during Year 3.