School practices and education policies are often influenced by various research, nonprofit, and philanthropic organizations. To help understand their influence, this paper provides a framework accounting for the variety of school improvement organizations (SIOs), and summarizes debates regarding their potential benefits and risks. We categorize SIOs as providing (1) direct school support, (2) research/advocacy, or (3) funding—each with a variety of organizations underneath them. Researchers highlight how SIOs take innovative risks, create improvement networks, and transform school practices. However, they also emphasize the danger of creating challengers to public institutions, the possibility of state retreat, and loss of community input. The paper concludes with suggestions for assessing SIOs’ outcomes, using this framework for future studies, and addressing critics’ concerns.