The two studies reported here tested whether a classroom-based psychological intervention that benefited a few African American 7th graders could trigger emergent ecological effects that benefited their entire classrooms. Within a classroom, the greater the density of African American students who participated in the intervention exercise, the higher the grades of all classmates on average, regardless of their race or whether they participated in the intervention exercise. Benefits of treatment density were most pronounced among students with a history of poor performance. Results suggest that the benefits of psychological intervention do not end with the individual. Changed individuals can improve their social environments, and such improvements can benefit others regardless of whether they participated in the intervention. These findings have implications for understanding the emergence of ecological consequences from psychological processes.