The term “21st century competencies” means different things to different people, and descriptions of these competencies rarely match one another exactly. Our purpose is not to provide a comprehensive catalog of 21st century competencies but to explore the challenge of assessing such outcomes, which are not widely measured and are not always amenable to the traditional assessment formats used for academic achievement tests. For this purpose, it is important that we identify a diverse set of 21st century competencies, not that we identify all such outcomes. It is also important that we select competencies that illustrate a broad range of assessment approaches.