Because the pandemic exacerbated chronic absenteeism in many parts of the country, the need to understand how schools can improve student attendance has never been greater. Accordingly, this study breaks new ground by examining high schools' contributions to attendance after accounting for individual students' prior absenteeism and other observable characteristics--that is, their "attendance value-added." To gauge the validity and reliability of this new indicator of school quality, Jing Liu of the University of Maryland analyzed more than a decade of data on student attendance, reading and math achievement, and long-term outcomes, such as college enrollment. Findings reveal: (1) Conventional student-absenteeism measures, including chronic absenteeism rates, tell us almost nothing about a high school's impact on students' attendance; (2) Like test-based value-added, attendance value-added varies widely between schools and is highly stable over time; (3) There is suggestive evidence that attendance value-added and test-based value-added capture different dimensions of school quality; and (4) Attendance value-added is positively correlated with students' perceptions of school climate--and, in particular, with the belief that school is safe and behavioral expectations are clear. [Foreword written by Amber M. Northern and Michael J. Petrilli.]