Multi-Tiered Systems of Support (MTSS) are frameworks used to assess individual needs of students and the supports needed to meet those needs. An MTSS is complex with components which impact core instruction, curriculum, formative assessment, interventions, summative assessment, and problem solving. All of these components are a part of a school's culture, and the success of this framework is dependent upon the leadership in a school. This study is important because it addresses the complexities of assessing individual student needs and the planning required to meet those needs. The purpose of this research was to study the implementation an MTSS with emphasis on school culture and leadership. A case study design was used within a quantitative and qualitative framework to study the essential character of a Multi-Tiered System of Support and its impact on school culture and leadership. Findings from this research indicate the importance of four mindset shifts relative to implementation of an MTSS including shared ownership, success for all, data-informed decisions, and collaboration. Transformational leadership was found important during MTSS implementation. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]