In 2007, Activity Based Learning (ABL), a child-centered, activity-based method of pedagogical practice, transformed classrooms in all of the over 37,000 primary-level government schools in Tamil Nadu, India. The large scale, rapid pace, and radical nature of educational change sets the ABL initiative apart from most school reform efforts. Interested in understanding how this movement achieved such success, we conducted oral history and ethnographic interviews, as well as an extensive review of reform documentation, to develop a historical case study of the ABL initiative. In this article, we present one of the findings of this study, arguing that the pursuit of ABL in Tamil Nadu was characterized by varied types of bureaucratic activism. State-level administrators, whom we consider bureaucratic activists, engaged strategies for change that combined both movement-building tactics and the conventional tools of administrative power. These reformers became pedagogical experts, expended considerable time and effort promoting the method, and engaged in a participatory, grassroots approach to pursuing the ABL reform within the state education sector. The egalitarian spirit with which ABL was promoted appeared to contribute to a moral authority and good will that generated support even when administrators used traditional tools of bureaucratic power, including top-down mandates, to institutionalize the reform. Ultimately, we argue, in their bureaucratic activism to change the government schools these administrators contributed to visible shifts in the nature of bureaucratic practice itself.