Educators in the state of California have struggled to reduce the number of minorities being suspended and expelled annually and significantly improve overall school climate and culture. To address this area of improvement, educators have begun to turn to a proactive approach to improve overall school climate and culture at their sites by implementing the Positive Behavior Intervention & Supports (PBIS) framework. Similar to many other school-wide intervention programs, the principals' ability and his or her leadership behaviors usually make the difference in whether the intervention program will be successful or not. In this study, the researcher surveyed 51 principals that were participating in PBIS Cohort 1 located in the Central Valley of California to gather data related to principal leadership behaviors. Follow-up interviews were conducted by the researcher of 7 of the participating principals in this study. Finally, suspension data were gathered from a sample of participating schools where the number of suspensions was compared between pre implementation and post implementation of tier 1 PBIS. In this study, the researcher found shared decision-making and developing a "team concept" was essential to the implementation of PBIS. Level of implementation was significantly higher in schools where the principal made the decision to implement, rather than the district office. Also, there was an overall decrease in the number of suspensions (24.4%) in a sample of 13 schools. [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.]