Many attempts at bringing successful educational programs and products "to scale" as part of school reform, particularly in urban districts, have been disappointing. Based on the experiences of the Collaborative for Academic, Social, and Emotional Learning (CASEL) and reviews of literature addressing implementation failures, observations about failures to "scale up" are presented. These include persistent structural features in educational settings that are too often unrecognized, the perpetuation of a narrow and decontextualized "programs and packages" perspective, poor management of time and other resources, and inadequate attention to characteristics of the adults who must carry out planned reforms. Several assumptions essential for success are identified, including the need to incorporate social and emotional learning as an integral part of academics and the ways in which diversity provides an ever-changing context for implementation. Concluding thoughts center around three points: the need to prepare professionals with the array of skills needed to lead efforts at scaling up school reform, the importance of an action-research perspective, and the need to better document the stories of educational innovation and scaling up efforts so that contextual details can enrich an understanding of what is required for success. (Contains 1 figure and 1 table.)