A quality education that promotes learning among all students is a prerequisite for an economy that increases opportunity, prosperity, and growth. School accountability policies, in which school performance is evaluated based on identified metrics, have developed over the past few decades as a strategy central to assessing and achieving progress toward this goal. The recent federal education law, the Every Student Succeeds Act (ESSA), requires states to add at least one measure of "school quality or student success" to its statewide accountability system. When students are absent from school, regardless of reason, they are not learning what is being taught--resulting in lower performance on coursework, course exams, and standardized tests and lower rates of high school graduation. Based on lessons learned from the No Child Left Behind Act and analyses based on the statutory and draft regulatory requirements under ESSA, we propose that states adopt chronic absenteeism as their measure of school quality or student success. Figures are appended and a Technical Appendix is included. A list of Hamilton Project Papers on Education is also included.