This Forum guide offers best practice suggestions on collecting and using student attendance data to improve performance. It includes a standard set of codes to make attendance data comparable across districts and states. There are real-life examples of how attendance information has been used by school districts. Chapter 1 discusses the objectives of the publication, and explains how the attendance taxonomy was developed. Chapter 2 provides a detailed description of each code in the attendance taxonomy. Chapter 3 discusses common challenges and effective practices related to attendance data, including developing an effective taxonomy; and ensuring needed data accuracy, communication, collaboration, planning, and automation. Chapter 4 shares examples of how states, school districts, and schools are using detailed attendance data to improve student attendance behaviors. The following are appended: (1) Attendance Codes by Reasons for Student Absences; (2) Differences in State Statutes Regarding Reasons for Student Absences; and (3) Recent Publications from the National Forum on Education Statistics. (Contains 2 tables, 2 figures, and 6 footnotes.) [A volunteer task force of the National Forum on Education Statistics produced this document.]