This white paper describes what a student assessment system could look like if built from the principles and best practices found in current educational research and effective educational systems in the U.S. and high-achieving nations around the world. With this paper, the Council of Chief State School Officers seeks to illuminate and enrich the discussion around comprehensive systems of student assessment and to help lead the development of more effective ways to assess student learning. It describes existing successful assessment systems that use a variety of ways to ensure student achievement in programs in our country and in high-achieving countries around the world. (Contains 5 endnotes.)