This ethnographic study utilized the theoretical frameworks of constructivism, cognitivism, and socio-cultural theories to examine how professional learning communities influenced the professional development of mathematics teacher knowledge and student achievement. This study sought to comprehend and interpret the behaviors, beliefs and values of the teachers toward their professional development and its impact on student achievement. Data collection consisted of participation observation, audio-taped semi-structured individual interviews, and focus groups. Qualitative data typological analysis was used to review data from four key components: teacher culture and behaviors, professional development for teachers, teacher collaboration through the use of professional learning communities, and connecting teacher efforts to improving student achievement. The results of the study suggested that teachers had a positive perception regarding collaboration and communication, shared leadership, and continued growth through professional development. Teachers and administrators may utilize the results of this study to influence professional learning communities to enhance professional development. The results of this study can lead to positive social change by providing a shared culture of collaboration which promotes a positive awareness among teachers that leads to improved instructional practice which can effect student learning. [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.]