The purpose of this two-phased, mixed-method action research study was to investigate the impact of a professional learning community's collective teacher efficacy and their practice of collective inquiry in closing the achievement gap of eighth-grade social studies English language learners. The research questions guiding this research: 1. How and to what extent will collective inquiry impact collective efficacy among teachers? 2. How and to what extent will a professional learning community's collective efficacy impact student achievement on the 8th-grade social studies state assessment for English language learners? Social cognitive theory and adult learning theory provided the theoretical foundation for this study, understanding how adults learn, including motivation factors and guiding principles for instituting effective andragogy practices (Bandura, 2001a; Knowles, 1968). Undoubtedly, much research reveals a positive correlation between collective efficacy and student achievement. However, minimal research exists examining the relationship between collective efficacy and diminishing the achievement gap (Goddard et al., 2017). The strength of the results of this study lies in the practical application of educators' daily work. In the context of the modern educational system, plagued by high stakes testing and unprecedented challenges resulting from the worldwide pandemic, education can feel like never-ending checklists of mundane activities and mandates. Success, at times, is defined by compliance rather than intrinsic and extrinsic motivation to ensure all students achieve success. This study's findings illustrated a correlation between collective teacher efficacy and continuous cycles of collective inquiry in closing the ELL achievement gap. While this study's results are limited, the findings are significant and worthy of review and should ignite future studies. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]