This study assessed aspects of construct validity of the School-wide Universal Behavior Sustainability Index–School Teams (SUBSIST), a measure evaluating critical features of the school context related to sustainability of school-wide interventions. Participants at 217 schools implementing School-wide Positive Behavior Support (SWPBS) were administered the measure. A two-step cluster analysis was performed to classify schools based on responses to the 39 SUBSIST items. A two-cluster solution was obtained, with schools in one cluster (n = 139) obtaining significantly higher scores on SUBSIST items than schools in the other cluster (n = 78). The most critical item that contributed to cluster formation was the use of data for decision making. Results also showed that higher sustainability scores were associated with increased frequency of school team meetings, presentation of data to school staff, access to an external coach/consultant, and greater number of years implementing SWPBS. These results are discussed with regard to implications for sustaining school-wide interventions.