Since the beginning of the Positive Behavior Interventions and Support (PBIS) program in the Study School District there has not been an evaluation of its effectiveness in reducing student discipline referrals and student suspensions and its success in promoting a positive learning environment leading to improved academic achievement. This study determined the effectiveness of the Positive Behavior Interventions System (PBIS) in the Study School District. It focused on determining the fidelity and consistency of implementation of PBIS in the District, the effect of PBIS on reduction of office discipline referrals and student suspensions from school, teacher attitudes toward implementation of PBIS, teacher morale since inception of PBIS, and parent perceptions of the effectiveness of PBIS in promoting positive student behavior. The results of this mixed methods study determined that there was a difference in the number of office discipline referrals during the four years since implementation of PBIS. The study also determined there was a difference in the percentage of referrals in the three major types of categories of office discipline referrals; school regulations, violent, and nonviolent. When the study analyzed the standardized test scores grades third through seventh and high school, did not evidence a measureable difference in student academic achievement based on ISAT performance during the four years following the implementation of PBIS. However, eighth grade did evidence a measureable difference in student academic achievement. Finally, the study determined there was not a measureable positive perception by staff and parents of PBIS with the exception of one statement on a Likert Scale survey. [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.]