This Campbell systematic review sought to examine the effects trauma-informed schools on trauma symptoms/mental health, academic performance, behavior, and socioemotional functioning. Trauma-informed approaches include programs, organizations, or systems that realize the impact of trauma, recognize the symptoms of trauma, respond by integrating knowledge about trauma policies and practices, and seeks to reduce retraumatization. At least two of the three key elements of a trauma-informed approach must have been present: (1) workforce development; (2) trauma-focused services; and (3) organizational environment and practices, which differ from trauma-specific interventions designed to treat or otherwise address the impact/symptoms of trauma and facilitate healing. Although the authors conducted a comprehensive search to find studies testing trauma-informed approaches in schools, no studies met the inclusion criteria, indicating that there is a lack of evidence of trauma-informed approaches in schools.