There is an emerging body of literature that places importance on the behavior of leaders of 21st-century schools. Research shows that the behavior of school leaders has a major impact on the effectiveness of a school. The effectiveness of a school is impacted by teacher motivation, and teacher motivation impacts student achievment. Successful school leaders have been found to possess a number of specific skills and attributes necessary to lead effective schools; thus, it is vital that school leaders strive to understand, value, and implement competencies necessary for achieveing success. This study approces excellence in leadership by examining 13 core competencies that school leaders must possess to remain successful in 21st-century schools. The 13 core competencies that inform the behavior of leaders are visionary leadership, curriculum and instruction, assessment, reflection, unity of purpose, diversity, inquiry, collaboration, professional development, professionalism, instructional leadership, organizational management, and learning community.The purpose of this study was to investigate: (a) the extent to which principals percieved that they valued and exhibited behaviors informed by the aforementioned core competencies, (b) the extent to which teachers percieved that principals valued and exhibited behaviors informed by the core competencies, and (c) the relationship, if any, between teacher perceptions and teacher motivation. The Leadership Behavior Inventory and the Attitude Toward Teaching Survey provided data for the research.It was hypothesized that the higher the teachers' perceptions were regarding principal leadership behavior the stronger the teachers' motivation would be. Data found that teachers were more likely to have higher self-efficacy, collective efficacy, and intrinsic motivation when they perceived that principals valued and implemented behaviors informed by the 13 core competencies. This confirms past research, showing that that the 13 core competencies are critical in creating transformational leaders within 21st-century schools.