A major concern for policymakers around the world is how to design an entire system of education that provides high quality teaching and learning outcomes. This paper aims to make a significant contribution to this debate by looking closely at the middle part of education systems -- the regional, district, and sub-district level -- as a critical part of the 'machine' for quality teaching and learning at scale. This working paper is part of a joint venture between the UNESCO International Institute for Educational Planning (IIEP), Education Development Trust, and the Education Commission in researching and strengthening roles at the middle tier of education systems. This review sees the potential of these middle tier leaders as a cadre of change agents who work directly with schools and teachers, and who are dedicated to instructional change and professional learning. [This report was co-produced by the Education Commission.]