The development and scale-up of school improvement networks is among the most important educational innovations of the last decade, and current federal, state, and district efforts attempt to use school improvement networks as a mechanism for supporting large-scale change. The potential of improvement networks, however, rests on the extent to which they can thrive in the turbulent world of U.S. education. In this article, we adapt a model of innovation scale-up and apply it to the problem of scaling-up educational networks. The framework identifies the constituent components of networks and environments, and the relationship between them. We demonstrate the framework's utility by illustrating the relationship between two prominent educational networks--the Success for All Foundation and America's Choice--and the educational environments in which they operated at two different points in time. Results suggest that without robust environmental support, networks are prone to a high degree of uncertainty and unpredictability. (Contains 1 table, 1 figure, and 16 notes.)