You may have seen this op-ed from the New York Times: Want to Fix Schools? Go to the Principal's Office by David Leonhardt.

To anyone working in or with schools, the position in this article is not surprising: effective schooling begins with effective school leadership. While teachers are the engine that drives a school, it is the principal as well as other formal and informal leaders that work to support teachers and improve instruction. 

We need to focus on supporting school leaders by giving them the tools they need to affect change. Principals need to be supported in their position and provided meaningful professional learning opportunities. The CALL Team has been working in this capacity for several years now, including with principals from Chicago Public Schools (where this Times article focuses).