English language learners (ELL students) were not attaining and maintaining sufficient proficiency at public schools in Northern California, as measured by students' achievement scores on state and district assessments. The purpose of this quasi-experimental research was to determine whether there were differences in academic language arts achievement of ELL students after increasing the use of combined professional learning community (PLC) teaching/learning strategies, as opposed to the teaching/learning strategy of direct scripted instruction only. Specifically, the study was developed to explore the changes in achievement scores on the Standardized Testing and Reporting (STAR) test scores for area districts across 5 years of increasing PLC implementation. The independent variable was academic year (5 levels) and represented increased use of PLCs. The dependent variable was the academic language arts achievement scores of the ELL students from the STAR test. The theoretical basis for this study was cooperative learning theories as they relate to PLCs. The study involved Northern California schools with ELL students in kindergarten to Grade 6 (N = 308). Bilingual or emergent classrooms were not included specifically, but students were speakers of other languages. A repeated-measures analysis of variance (ANOVA) was used to examine achievement on the STAR across the years before and after PLC implementation. STAR scores, the end-of-year achievement tests, were compared before and after PLC implementation. Results showed that there were significant improvements in STAR performance after PLC intervention. This study may lead to positive social change by providing practitioners in the study districts with research based findings that can be used to improve ELL instruction and teaching strategies through PLC application. [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.]