This study examined the relationship between principal leadership behavior and student achievement in South Dakota secondary schools. Teacher perceptions of principal leadership were measured using the Transformational Leadership Behavior Inventory. Student achievement data came from the Dakota Standardized Test of Educational Progress. The study analyzed the relationship between leadership and achievement, leadership and improvement in achievement over time, individual leadership components and improvement, and a model containing leadership, school factors, and achievement. The goal was to determine the influence of principal leadership on student performance under the accountability standards of No Child Left Behind.