This article reports the effects of a comprehensive elementary school-based social-emotional and character education program on school-level achievement, absenteeism, and disciplinary outcomes utilizing a matched-pair, cluster-randomized, controlled design. The Positive Action Hawai'i trial included 20 racially/ethnically diverse schools (M enrollment = 544) and was conducted from the 2002–03 through the 2005–06 academic years. Using school-level archival data, analyses comparing change from baseline (2002) to 1-year posttrial (2007) revealed that intervention schools scored 9.8% better on the TerraNova (2nd ed.) test for reading and 8.8% on math, that 20.7% better in Hawai'i Content and Performance Standards scores for reading and 51.4% better in math, and that intervention schools reported 15.2% lower absenteeism and fewer suspensions (72.6%) and retentions (72.7%). Overall, effect sizes were moderate to large (range = 0.5–1.1) for all of the examined outcomes. Sensitivity analyses using permutation models and random-intercept growth curve models substantiated results. The results provide evidence that a comprehensive school-based program, specifically developed to target student behavior and character, can positively influence school-level achievement, attendance, and disciplinary outcomes concurrently.