After expanded coverage of the school system, ensuring that students learn at school has become the priority in many developing countries. This case study analyzes Brazil's experience in developing its student assessment system. Brazil's story should prove particularly interesting to those aiming to understand how a large (and, in this case, federal) country can successfully implement extensive reforms of its assessment system. In Brazil's case, the reforms involved developing a comprehensive policy framework for the support and funding of assessment activities; creating an autonomous, federal institution to be in charge of key assessment programs; ensuring stable and sufficient funding; and developing in country capacity to carry out assessment tasks. In Brazil's case, the reforms involved developing a comprehensive policy framework for the support and funding of assessment activities; creating an autonomous, federal institution to be in charge of key assessment programs; ensuring stable and sufficient funding; and developing in-country capacity to carry out assessment tasks. Several factors allowed for these reforms to take hold. Among the most important were: stable political leadership; making education, and the need to monitor education quality, a national priority; and partnerships with nongovernmental institutions. Sustained leadership across political coalitions also is important to ensure stable support for assessment initiatives. Finally, successful reforms require the participation of many stakeholders, including government and nongovernmental organizations, as well as international donors.