This mixed method exploratory sequential study examined Illinois high school administrators' perceptions of Senate Bill 100 implementation and the type of professional development provided for staff. This study examined administrators' perceptions on the mindset of staff, effects on student discipline, and professional development offered and utilized in Illinois high schools. Data in the qualitative phase was collected by interviewing six administrators to explore their experiences with Senate Bill 100 implementation. After the qualitative data was analyzed for themes, a quantitative survey was created, and data was collected from 69 respondents. Administrator responses in the quantitative phase were analyzed based on administrator demographics and district characteristics. The results of the study exposed statistically significant differences in all domains based on demographics and district characteristics. The results of the qualitative and quantitative phases were combined to identify generalizations. Findings in this study demonstrated that student discipline did not decrease and disproportionality in discipline still exists among low-income students and students of color, despite Senate Bill 100 implementation. Furthermore, this study showed that administrators perceive teachers as inadequately prepared for the paradigm shift from retributive to restorative discipline. The study concludes that professional development related to social emotional learning, restorative practices, and racial literacy was used more by administrators than teachers. Implications for schools, research and policymakers are also presented. [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.]