This chapter begins by distinguishing among prevention, intervention, and promotion efforts, giving particular attention to how these processes operate in the context of schools. One example of a school-based, evidence-based practice – City Connects – is used to illustrate how prevention, promotion, and intervention can be operationalized in the contexts of schools and their local communities. As a clinical/public health model, City Connects is responsive to every child in the school, without an exclusive focus on either the subset of students who are in severe crisis or those who are highest performing. The authors argue that prevention-in-action requires working across polarities, such as intervening at both the individual and group levels, targeting challenges while fostering strengths and interests, and promoting healthy development while simultaneously intervening in existing difficulties. The chapter concludes with a summary of challenges and possibilities in implementing high-quality prevention and promotion approaches, such as developing a theory of change based on developmental science that includes measurable outcomes.