Is there a school leader anywhere who hasn't been directed, or at least encouraged, to "analyze the data" and practice what has been termed "data-driven decision-making"? Today's principal is expected to be able to skillfully collect, organize, analyze, interpret and use a variety of data in order to improve instruction, services and programs for students and, ultimately, improve academic achievement and other student outcomes. As a result of this intense focus on data, school districts, universities and professional development providers are offering training and resources to meet this demand. However, amid all of this attention to data-driven decision-making, there has been a critical and consistent gap in the services provided to the principal: The "mind-set" required to apply new knowledge and skills in a way that results in improved outcomes for students. This article discusses the attributes of an appropriate mind-set for data-driven decision-making.