This paper outlines the genesis, limitations, and future directions for the Education Quality and Accountability Office (EQAO) in the province of Ontario. Recent assessment reforms are analyzed and examined in relation to broader Canadian and international literature. Research describing the impact of Ontario’s large-scale assessment programs on students, teachers, and the school system is also reported. The discussion outlines measures for strengthening large-scale assessment within the province and proposes a set of three overarching principles to guide future assessment-led reform.