Education ministries throughout the world are integrating educational assessment into their education reform processes. Education reform is not a straight-line activity, and assessment can both inform the discussion on policy reform and give an indication of the effectiveness of policies that have been implemented. Three different types of assessment are used in the educational process: classroom assessment, examinations and system-level assessment. Each type has a different purpose. While the focus of both classroom assessments and examinations is to measure the learning outcomes of individuals, for system-level assessment the focus is to describe the characteristics of the population as a whole so that policies can be designed and put in place to target observed areas of weakness. This paper attempts to demonstrate how system-level assessments can inform education policy by drawing on examples of countries that have used assessment programs in education reform processes.