This research design was a mixed methods embedded study with a quasi-experimental component in the quantitative portion identifying the teachers and students as independent variables and the Professional Learning Communities (PLCs) that are aligned with teacher effectiveness and student achievement as the dependent variables. The confounding variables which may have negative or positive impact are class size, heterogeneous student groups, and the context taught to the students to increase student achievement. This study was conducted in a western suburb of Chicago with a culturally diverse population in three elementary schools with students in grades kindergarten through fifth grade. Students' math and reading scale scores as quantitative data from the Star 360 assessments were analyzed based on the teachers participating in PLCs to determine if there was an impact in the test scores. The results showed that there were significant differences in both the reading and math scores indicating that the teachers' participation in the PLCs did have a positive effect on student achievement. A teacher survey with quantitative questions in four key categories including Communication, Collaboration, Teaching and Learning, and Professional Development identified that teachers' responses were consistently in agreement except for a question on whether they disagreed when having PLC strategy discussions where there was a statistical difference in the responses. The four qualitative questions were analyzed using the grounded theory by developing themes that showed positive agreement among the teachers about the value of their participation in PLCs to enhance their professional development, teamwork, and most importantly, student achievement. [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.]