This report provides a systematic review and empirical evidence related to the experiences of middle-income countries and economies participating in the Programme for International Student Assessment (PISA), 2000 to 2015. PISA is a triennial survey that aims to evaluate education systems worldwide by testing the skills and knowledge of 15-year-old students. To date, students representing more than 70 countries and economies have participated in the assessment, including 44 middle-income countries, many of which are developing countries receiving foreign aid. This report provides answers to six important questions about these middle-income countries and their experiences of participating in PISA: What is the extent of developing country participation in PISA and other international learning assessments? Why do these countries join PISA? What are the financial, technical, and cultural challenges for their participation in PISA? What impact has participation had on their national assessment capacity? How have PISA results influenced their national policy discussions? And what does PISA data tell us about education in these countries and the policies and practices that influence student performance? The findings of this report are being used by the OECD to support its efforts to make PISA more relevant to a wider range of countries, and by the World Bank as part of its on-going dialogue with its client countries regarding participation in international large-scale assessments.