Successful schools that provide positive, productive, and vibrant teaching and learning environments do not occur by accident. Instead, the most effective schools are led by principals who are equipped with the skills and possess the attitudes required to be exceptional school leaders. The good news is there is a growing research base that clearly defines the dispositions, skills, and knowledge needed for effective school leadership today. The disheartening news is that few educators are being measured against these criteria prior to becoming principals. States play a critical role in determining who leads the country's schools. Individual states control the two most important levers to ensure the quality of principals--principal preparation program approval and principal licensure oversight. Yet few states are exerting their authority and efficiently using these two levers to improve educational outcomes for children. Recognizing that states act as key gatekeepers to improve educational outcomes for children, it is imperative that states take immediate action to guarantee that each and every school is led by a high-quality principal. In this report, the authors analyze state policies and requirements for principal preparation approval and certification in a sample of 16 states--eight of which are "lagging," and eight that are "leading" in their efforts to act as gatekeepers to ensure that schools are led by effective leaders. An effort was made to select a large pool of states to reflect a range of practices and policies, as well as to provide variation in the context, for example, geographic representation, student demographics, and population size. State websites for sources to the three tables in this report are appended. (Contains 36 endnotes.) [For related article, "Review of "Gateways to the Principalship"," see ED528638.]