One of many problems schools face today is the ability to implement effective professional development (PD) for staff. Research on this topic has shown a lack of follow through on the school district's part to offer consistent and effective PD to our teachers (Daegan & Bean, 2015). With the adoption of Smarter Balanced state testing in New Hampshire and competency-based education (CBE) practices in select districts, appropriate and effective PD must be offered to teachers and administrators (Desimone, Porter, Garet, Yoon, & Birman, 2002). Participants for this study included elementary teachers and administrators from a school district in New Hampshire that is implementing a K-12 CBE system. Using a mixed methods sequential explanatory design, data was collected and analyzed to determine the effects of the district's PD program on teacher and principal self-efficacy. The results from this study indicate the PD program had some positive effects on teacher self-efficacy and that principal self-efficacy was also positively impacted. Results also showed that an important aspect of the positive effect of the PD process on self-efficacy for teachers and principals was the ability of people to collaborate with their peers. Two major concepts were critical in the analysis of the data: Fullan's (2007) framework of the change process and Somech and Oplatka's (2016) concept of organizational citizenship behavior. By examining the impact a PD series had on teachers' and administrators' self-efficacy, it was determined how a PD series should be designed so that it will support a district's transition to an educational initiative. [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.]