This article presents findings from a study of the minimum conditions needed to scale a previously successful model of high school reform in New York City. Most studies of scale work backward to identify conditions that were in place when scale was successful, rather than identifying those that were minimally required, and thus more likely to be achievable across settings. Findings from this study suggest that only three minimum conditions are needed for scale -- adequate knowledge of the model; an appropriate environment; and a working feedback loop -- when these conditions interact in a functioning, self-adjusting ecosystem.