The role of assessment in education has grown greatly over the past few decades, a trend that has two major manifestations. One is the rapid increase in the number of countries and other jurisdictions either participating in international surveys (tests) of learning or initiating their own system-wide assessments; or both. The other is the ever-rising importance of assessment to hold systems and their key actors (notably teachers) accountable for education outcomes. The recent renewal by the world’s nations and lead international organizations at Incheon, Republic of Korea of their commitment to an education “of quality” for all by 2030 and the upcoming global commitment to the new Sustainable Development Goals will now ‘raise the bar’ for education in terms both of equity and of how to perceive “quality,” which now requires a much more relevant lens. Measuring progress towards these goals will begin with the assessment of learning, to determine both whether students are acquiring the required knowledge and competencies and whether a system is providing students with the appropriate education to acquire these outcomes. While assessment will be vital to this process, there is a severe double risk that systems and their partners will continue to rely excessively on tests to drive its reforms. First, most major tests do not reach all students and focus on just a few subjects – primarily Reading and Mathematics, and sometimes Science –, with the common result of a narrowing of the curriculum and of other distractions to the education process. Similarly, with rare exceptions, such tests neglect the broader range of personal competencies, such as the acquisition of new knowledge using a variety of methods, and the practical application of the basic knowledge and techniques students learn in school. The second risk is the continued failure to coordinate assessment with the other major functions of the education system – perhaps most notably, the curriculum, operating instead in relative (if not total) isolation. For assessment to be of high quality and relevant, and for it to inform real improvements to the overall education system and its outcomes, it must be in full and functional harmony with a system’s curriculum, teacher training and support, texts and materials, planning, budgeting and all other departments. The present report explores the ways in which assessment is vital to education and posits means by which it can connect effectively to the other key education functions to drive a national system forward to 2030.