Background: Adverse Childhood Experiences (ACEs) can impair health and other outcomes. To obtain district-level data about the prevalence and impact of ACEs in Chicago Public Schools (CPS), we advocated for CPS to add a short ACE screener to the 2017 Youth Risk Behavior Survey (YRBS) and analyzed the results. Methods: Responses to the screener were scored zero, one, or two ACEs. Student scores for violence and victimization, substance use, sexual health risk, mental health, housing insecurity, physical health, grades, and multiple risk/high vulnerability (those students in the top 20% of affirmative responses) were correlated with ACE scores for categories and individual items. Results: Among 1883 student respondents (response rate 73%), there were 17.8% affirmative responses for experiencing physical abuse and 19.8% for witnessing domestic violence; 20% reported at least one ACE and 8% both. A significant dose-response was found for behaviors, experiences, and sleep by ACE scores. Conclusions: ACEs were common among CPS high school students and associated with many negative behavior and health-related outcomes. Increased awareness of ACEs and their impact among all school personnel can inform and strengthen the development of safer, more supportive, and trauma-informed schools that help all students and families thrive.