Effective leadership does not depend on a set of attributes that a single individual possesses. Instead, the search for one best heroic leader should be replaced with the search for and investment in a number of superheroes: a League of Leadership. Those who create a leadership league don't explore individual skills, but collective practices, such as determining how to engage teachers and staff members and how to lead a school of teachers who are invested in improving instruction. The authors suggest that how effective a leader a principal is lies not in his or her role as a superhero, but in his or her day-to-day collaborative processes of inquiry and action. In this article, the authors discuss a collaborative inquiry-action cycle which consists of practices that principals can use to create empowering opportunities for all those in a school to become a league that contributes to student learning. The cycle is a planned, purposeful, and democratic process for identifying, framing, and accepting responsibility for a problem of practice; for articulating a theory of action, decision making, and action; for gathering data and evaluating effects of actions; and for reflecting, revisiting, and reconceptualizing the problem of practice. The authors illustrate the process by using the example of Lee, who has just assumed the principalship of the underperforming Marshall Middle School. (Contains 2 figures.)