The main objective of this qualitative case study was to examine the perceptions of secondary school principal's effectiveness and its perceived effect on student outcomes. This study focused on the collected data of teachers' perceptions and the leadership style of principals. This is essential to understand teachers' perceptions and a principal role as a leader; including adding to current literature in the field of education. An additional focus was to examine the impact of principals' leadership style as related to student achievement. The following research questions were addressed: (1) What are the perceptions of school administrator's leadership skills that negatively affect student outcomes? (2) What are the perceptions of school administrator's leadership skills that positively affect student outcomes? To examine the research questions, this study used the transformational leadership model as a theoretical basis for determining the relationship between teacher perceptions of school principals' leadership style and student achievement. The findings of this study suggested that a transformational leader is perceived as a more supportive school principal. Therefore, principals' should be cognizant of transformational traits within their own leadership style of leadership (Kornbluh, 2015). Consistent with the reviewed literature and current findings of this study support the significance of teachers' perceptions. The findings also, supported the reviewed literature in that a principal's leadership plays a vital role in the environment of the school and the morale of teachers (Grisby, 2015). Implications for practice and recommendations for further research are included. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]