This dissertation study aimed to examine the relationship between Tier 1 Positive Behavioral Intervention and Supports (PBIS) implementation fidelity and the academic (e.g., MAP Growth scores) and behavioral outcomes (e.g., major office discipline referrals, suspensions). High quality PBIS implementation fidelity has been linked with improved standardized test scores and decreased instances of major office discipline referrals, in-school suspensions, and out-of-school suspensions for students with and without behavioral difficulties. However, no research has been done on the impact of PBIS implementation fidelity on students with ADHD. It is estimated that at least 40% of students with ADHD require at least one school-based support (e.g., behavioral interventions, academic interventions, an Individualized Education Plan [IEP]), but less than half of students with ADHD receive formalized special education services. Tier 1 implementation fidelity was selected because these supports are received by all students with ADHD regardless of special education eligibility. The purpose of the current study was to examine the relationship between PBIS Tier 1 implementation fidelity and the educational outcomes for students with behavior similar to individuals with ADHD using a sample of elementary and middle school students from a school district in Nebraska. The data analytical strategies in this study included descriptive statistics and three-level hierarchical linear models. The results elucidate the impact of PBIS implementation on the outcomes for these students. [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.]