Shared leadership

noun

A leadership approach in which areas of decision making and responsibility are not held by a single individual but shared by several. The phrase can carry an inherent focus on an individual leader or leaders who share their power with others, unlike collective leadership, for example, which emphasizes more the team unit, or distributed leadership, which emphasizes more a discrete division of leadership roles.

Also worth noting: this phase was originally coined—and is more likely to be used—outside of education/school-related contexts, for example referring to the leadership of companies, military organizations, or government entities.