For this study, I explored the degree of implementation of the Positive Behavioral Interventions and Supports (PBIS) framework and the existence of disproportionality of formal school disciplinary responses to behavioral occurrences by race/ethnicity, sex, special education status (SPED), and socioeconomic status (SES) of students. Further, I investigated the relationship between a school's degree of implementation of PBIS and the existence of disproportionality by race/ethnicity, sex, SPED, and SES, and investigated the differences in the existence of disproportionality in schools that fully implemented PBIS and schools that did not fully implement PBIS. Literature exists on PBIS implementation and, separately, on the existence of disproportionality in school discipline; but this is the first study of their intersection. Generally, the existing literature on PBIS implementation shows full implementation is associated with a decrease in the overall number of behavior occurrences. In addition, the literature on the disproportionality of discipline suggests certain student groups are overrepresented in school discipline, specifically non-White, male, SPED, and low SES students. Implementation was measured using the School-Wide Evaluation Tool (SET). Disproportionality was calculated using the enrollment and discipline data entered into the Student Information System (SIS) for each school. This study included 16 schools from one Midwest state, with 7,124 enrolled students in kindergarten through twelfth grades. The approximate percentages of enrollment for the listed demographic groups: non-White 42%, male 52%, SPED 14%, low SES 62%. There are four main findings in this study. First, nine of the 16 participating schools fully implemented PBIS, which means seven did not. The second finding is that non-White, male, SPED, and low SES students were overrepresented in reported behavior occurrences. The third finding is there was no correlation between the implementation of PBIS and a lesser existence of disproportionality in school discipline by race/ethnicity, SPED, and SES, and a positive, moderate correlation when broken down by sex. The final finding showed no significant difference in disproportionality in reported behavior occurrences in schools that fully implemented PBIS and those that did not fully implement PBIS. This study confirms existing literature on the overrepresentation of certain student groups in reported behavior occurrences, including non-White, male, SPED, and low SES students (Bowditch, 1993; Boneshefski & Runge, 2014; Caldwell et al., 2020; Garibaldi, 1979; Gregory et al., 2010; Hamilton, 2019; Kaufman et al., 2010; Lacoe & Manley, 2019; Maag, 2012; Mizel et al., 2016; Montgomery, 2012; Okonofua et al., 2016; Predy et al., 2014; Roch & Edwards, 2017). This study also confirms that PBIS implementation tends to be stronger in elementary settings (Akos et al., 2015; Bailey et al., 2015; Boneshefski & Runge, 2014; Bradshaw et al., 2010; Burke et al., 2012; Cressey et al., 2014; Grimaldi & Robertson, 2011; Lacoe & Manley, 2019; Smolkowski & Strycker, 2014). The ultimate goal of PBIS implementation is to meet the behavior support needs of all students; however, I found that certain student groups continued to be overrepresented in school discipline data, even with full implementation of PBIS. [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.]