Principals who are strong, effective, responsive leaders help to inspire and enhance the abilities of their teachers and other school staff to do excellent work. Such principals also tend to retain great teachers and create opportunities for them to take on new leadership roles. This leads to the following key question: What can state policymakers do to help ensure that schools have excellent principals who advance teaching and learning for all students? The answer: Quite a bit, actually. The research informing this report identifies three crucial areas leaders across all states can usefully consider as they seek answers to this key question: (1) State policy agendas that address school principals along with other priorities; (2) State policy levers available to state leaders as they attempt to identify and train aspiring principals and support those already on the job; and (3) the contextual factors within states and local communities that affect how state policies or initiatives for principals are likely to unfold in practice. The report emphasizes that every state faces a unique blend of educational, political and financial circumstances and that, therefore, each state's approach should fit its needs and particularities.