The purpose of this study was to examine data from the Early Childhood Longitudinal Study: Kindergarten Class of 1998-99 (ECLS-K) report, identify questions and statements that correlate to the dimensions of professional learning communities (PLCs), and determine the effect PLCs have on student achievement based on the ECLS-K data. In addition, the rationale for doing this research was to measure growth in student achievement over time. A multilevel growth model was used for this research. Univariate analysis was conducted in order to reveal frequencies and percentages associated with teacher responses. Bivariate analysis was applied in order to determine the inter-correlations between the fourteen variables. Once the inter-correlations were determined from the bivariate analysis, principal component analysis was applied in order to reveal the theoretical relationship between the variables. Through the use of principal components a set of correlated variables is transformed into a set of structure coefficient: support and collaborative. Finally, a multilevel growth model was used in order to determine the effect that each variable within the support and collaborative structure coefficients had on student achievement over time. This study revealed a number of variables within the ECLS-K report that correspond to the dimensions of PLCs have a statistically significant effect on student achievement in math and reading over time. This study demonstrated that support and collaborative variables within PLCs have a positive effect on both math and reading IRT achievement from 3rd grade to 5th grade. [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.]