This study examines the impact of 2 professional learning community (PLC) classroom practices on the English Language Arts achievement of California's most at-risk subgroups between selected higher- and lower-performing elementary schools in a southern California school district. The conclusions from this study agree with the body of research, suggesting that Higher Performing schools frequently monitor student achievement and use data to recognize, intervene, and adjust instruction. PLC practices were presented through the lens of the National Center for Educational Accountability's Best Practice Framework. This study focused on 2 classroom practices: Monitoring: Compilation, Analysis, And Use of Data, and Recognition, Intervention, and Adjustment. Five elementary schools were selected for participation in this study. The five schools selected for the study are demographically equivalent (65% or more English Language Learners, Socio-Economically Disadvantaged, and Hispanic/Latino), but have disparate levels of sustained high student achievement results in English Language Arts on the California Standards Test. Three schools were Higher Performing, and two were Lower Performing. The survey was administered to 92 teachers and 8 administrators. Data from the survey responses were compared with participants' school type, Type of Educator, and demographic variables, and were tabulated using standard summary statistics. General findings demonstrate a significant difference in the level to which Higher Performing Schools monitor student learning and recognize, intervene, and adjust compared to Lower Performing Schools. Overall, teachers and administrators agreed that student learning is monitored, but a strong difference was found based on school designation as Higher or Lower Performing. Generally, teachers versus administrators reported substantially different levels of classroom use of Recognition, Intervention, and Adjustment, but no difference was nosed on school designation. Little or no relationship was found between either practice and experience level or gender of the practitioner. Implications of these findings underscore the need to identify and implement PLC best practices that have demonstrated effectiveness for California's most at-risk subgroups in English Language Arts. Districts and schools must ensure periodic formative and summative standards-based assessments are in place. Practitioners must have the capacity to closely monitor results for at-risk students, and appropriately provide recognition, intervention, and adjustment so that all students master English Language Arts standards. Ten appendixes are included: (1) The National Center for Education Accountability's Best Practices Framework; (2) Classroom-Level Survey Packet; (3) School-Level Survey Packet; (4) Principal Directions for Survey Administration; (5) Volunteer Teacher Directions for Survey Administration; (6) Procedure Steps of Data Collection; (7) Institutional Approvals; (8) Identification of Self-Audit Questions Reflective of the Critical Attributes; (9) Renumbering of NCEA's Self-Audit Questions; and (10) Demographic Characteristics for the Teacher and Administrator Samples. (Contains 1 figure and 16 tables.) [Ed.D. Dissertation, Pepperdine University.]