This paper examines the ways in which entities external to schools, in this case for-profit educational management organizations (EMOs), can influence the development of school professional community. Drawing on case studies of six charter schools operated by three EMOs, this paper examines the presence of the five elements of professional community, supports and barriers to the development of professional community, and the role of EMOs in influencing those supports and barriers. The paper reports the findings that EMO staff can influence professional community in important ways: through the design of their program, including the structures that they set up for the use of time and staffing, and through their informal relationships with schools, including their roles as"cheerleaders," constructive critics, flexible keepers of the model, and reliable managers. Such findings can aid in understanding not only the role of EMOs but also the potential for other external organizations, such as the whole-school reform model providers and school districts, to promote positive moves in supporting the development of school professional community. They can also help EMOs develop their own educational approach. (Contains 39 references.) (Author)