The purpose of this study was to examine the effects of a school-wide attendance and truancy intervention and universal procedures (ATI-UP) on student attendance. Student attendance was measured through average daily attendance and the percentage of students who would be considered chronically absent, i.e., missing 10% or more of school. The sample included 27 elementary schools in Oregon implementing school-wide positive behavior intervention and supports (SWPBIS) with varying levels of fidelity. Results indicate that schools can have a moderate effect on increasing average daily attendance (ADA) and a small effect on decreasing chronic absenteeism, although these results were not statistically significant. SWPBIS implementation did not act as a statistically significant moderator on the ATI-UP effects, although the treatment effect on ADA decreased with higher SWPBIS implementation. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]