Leadership matters. Principals are the primary drivers of school improvement and the best long-term investment to ensure effective teaching and learning at scale. Principals are central to State efforts to implement new college and career-ready standards, execute teacher evaluation and support systems and turn around low-performing schools. These reforms require principals to do their work differently, allocate their time in new ways and learn new skills. Many school leaders are overwhelmed by new expectations. Limited school leadership capacity is posing a real challenge to States in meeting educational goals since principals are the centerpiece of high-quality State policy implementation. There are four reasons for this reality--many States: (1) have an outdated vision of the principal role; (2) have not yet recognized the balance of new school leader responsibilities in State policies and programs, leaving far too much on principals' plates for one person to do well; (3) do not currently provide high-quality professional development and support; and (4) design policies that rely on principals for implementation without their input. As States continue to implement these reforms, they can create conditions for success by prioritizing school leadership. This brief is divided into four sections that address actions States may take in response to the four challenges outlined above: (1) The Principal Role: State policies prioritize school leaders' roles as instructional leaders and talent managers; (2) Distributed Leadership: State policies promote models of shared leadership that enable principals to spend their time on the most important activities and build a pipeline of future leaders; (3) Principal Management and Support: State policies encourage better and more targeted professional learning and support for school leaders, including from those who supervise principals; and (4) Principal Engagement: State policies are improved through ongoing engagement with the principals who are responsible for implementing reforms. This brief identifies some of the most important actions States can take to support principals. State actions can take many forms--direct and indirect--so policymakers may reflect on the political climate in the State to determine which type of influence will be most effective. Embedded throughout the brief are links to more information and case studies from leading States. The brief also includes self-assessment rubrics, which can be used by States to prioritize areas of focus.