With increased pressures on school districts to enhance student achievement, administrators are implementing professional learning communities (PLCs) as one method to improve student performance (DuFour & Eaker, 1998, Hord, 1997, Thompson, Gregg, & Niska, 2004). Educators working within a PLC experience a shared ideology, supportive conditions for collective inquiry, shared learning through collaborative teams, attention to professional development and learning, and a purposeful focus on student achievement (DuFour & Eaker, 1998, Hord, 1997). Little quantitative research has used standardized testing to measure the benefits of PLCs. This quasi-experimental, quantitative study found a statistically significant difference between value-added scores on the Tennessee Comprehensive Assessment Program in mathematics and reading/language arts as reported by the Tennessee Value-added Assessment System (TVAAS). Within the parameters of this study, the analysis from 2009 and 2010 revealed the difference in TVAAS scores for fourth and fifth grade students attending schools that implement professional learning communities was statistically significant compared to the value-added scores of students that did not attend PLC schools. The experimental group consisted of elementary or intermediate schools with a fourth and a fifth grade team working as a PLC for three or more consecutive years as defined by DuFour and Eaker's (1998) theoretical framework. The control group did not use PLCs. Three-year value-added scores in mathematics and reading/language arts were analyzed using a two-sample t test assuming unequal variances. The literature review and findings from this quantitative study support the idea that when educators work in PLCs, the effects are positive outcomes for 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.]