Data-driven decision-making (DDDM) requires educational leaders and teachers to monitor and evaluate programs and processes and link results to individual and organizational outcomes. A classroom teacher's ability to collect and review data, analyze data to identify trends and strategies for student achievement, and use data to determine and implement instructional practices that influence student achievement is important to school improvement. The purpose of this qualitative case study was to investigate whether elementary teachers' self-efficacy beliefs, human agency, participation in professional learning communities (PLCs) on DDDM, and their implementation of the DDDM process influence teachers' instructional practices. The theories that served as the framework of this study were data-informed decision-making (DIDM) and the Social Cognitive Theory (SCT). The target population was elementary teachers in a public school district in Eastern Mississippi. The researcher conducted a focus group with seven participants and in-depth semi-structured interviews with ten participants via face-to-face and video conferencing. Teachers who participated in the interviews and focus groups shared their experiences, which led to themes of teachers' perceptions of DDDM, the use of benchmark assessment data, challenges in using data to drive instructional decisions, the environment of PLCs, types of data discussed in PLCs, and collaboration and support for DDI being identified. The insights gathered from this study suggest the need for continued investment in professional development initiatives that promote collaborative practices, strengthen teachers' data literacy skills, and empower educators to leverage data effectively to inform instructional decision-making. Furthermore, the findings underscore the need for future research endeavors to delve deeper into the complex interplay between data, self-efficacy of teachers, and collaborative practices within PLCs, thereby informing evidence-based educational policies and practices to maximize student success. [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.]