The purpose of this study was to determine if the National Board Teacher Certification (NBTC) process was an effective form of professional development for teachers that would result in changing teachers' instructional practice resulting in improved student learning. The study also examined how a cohort of NBTC candidates impacted the non-NBTC teachers in a school and looked at how being part of a cohort impacted the NBTC candidates experience as they went through the process of NBTC. Data for this study were collected during the 2008-09 and 2009-10 school years at May Creek Elementary School in the Creekside School District. Interviews with the NBTC candidates, classroom observation data, a survey of all staff in the school, interviews with non-NBTC teachers, and student achievement data was collected and analyzed. The NBTC process requires teachers to engage in activities that are aligned with effective professional development as described by Sato, Wei, & Darling-Hammond (2008), Cohen and Rice (2005), and Guskey and Yoon (2009). Results indicate that the NBTC is a quality professional development experience for the candidates. The NBTC candidates described how the process required them to reflect deeply and analyze student work and their own instructional practice in order to find evidence of accomplished teaching. The non-NBTC colleagues also found that the NBTC candidates were focused on student learning targets, had knowledge about effective instructional practices, and contributed effectively to the professional collaborative experience for all teachers in the school. An unexpected finding was the impact of being part of a cohort as they went through their learning process. The NBTC candidates felt that they would not have been as successful or benefited from the experience to the degree they did without being part of a cohort in the same school. While the findings about the impact of NBTC on student achievement were not conclusive, they lead the researcher to conclude that further investigation on a larger scale would be valuable and may indicate a positive impact. [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.]