Deep and careful analysis of the collective work of teachers and school administrators as they embark on the development of innovative instructional programs, such as the International Baccalaureate's Middle Years Program (MYP), is essential to building models for 21st century education. Two theoretical frameworks, distributed leadership and social networks, have emerged in the educational research literature that as integrated by this study present leadership for school-based change and innovation efforts in terms of actions related to the school's central mission and emphasize the importance of social interactions for their enactment. This exploratory case study draws upon its integration of these theories to describe and understand leadership in action during the school-based design and early implementation of the MYP curricular master plan as well as the social networks underlying enactment of leadership actions. The study presents findings on two levels: educational theory and educational practice. In terms of theory, the study proposes that leadership tasks for the school-based development of academic programs are classified as curriculum design tasks and teacher support tasks. These tasks take on distinct social distributions that respond to the nature of the task and contextual factors explored in the study that influence its enactment. It is further proposed that integration of social network theory into its framework reshapes the distributed leadership model in two ways: it asserts the multiplicity of actors involved in leadership actions thus making the leader-plus aspect an unnecessary category in and of itself and it becomes the driving method for measuring and lens for understanding the social distribution of leadership tasks. On a practical level, the study highlights (1) the importance of coherence-building, collaborative design task for a systemic instructional vision, (2) the critical role of teacher support tasks that provide key resources for the successful enactment of design tasks, (3) the promotion of certain school- and team-level conditions that support collaborative processes, and (4) the existence of certain school-and team-level conditions that constrain teacher collaboration.