Schoolwide Positive Behavior Intervention and Supports (SWPBIS) is a tiered program that provides three levels of behavior and social-emotional support for students. Tier one is for all students, tier two is for some students in need of targeted or some additional intervention, while tier three is for few students who need the most intensive support (Center on PBIS, 2023b; Lewis et al., 2017; Simonsen et al., 2008; Sugai & Horner, 2002). Schools have increasingly implemented Schoolwide Positive Behavior Intervention and Supports (SWPBIS), but research suggests that few high schools have implemented SWPBIS when compared with elementary and middle schools (Feuerborn et al., 2015; Flannery et al., 2013). High schools have varying contextual factors that differ from elementary and middle schools, presenting distinctive challenges with the implementation process and fidelity of SWPBIS. This qualitative phenomenological study explores secondary teachers' perceptions of the school-wide and class-wide implementation process of SWPBIS at the high school level and its impact on students with disabilities and other health impairments. Additionally, this study examines secondary teachers' perceptions of effective discipline strategies and their perception regarding out-of-school suspensions. Findings suggest that inequitable practices of the SWPBIS may likely stem from personal beliefs and philosophy of SWPBIS, teacher autonomy in the classroom, lack of time and inconsistent implementation, and buy-in. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]