The purpose of this two-phase, sequential explanatory mixed-methods research study was to examine the correlation between kindergarten through fifth-grade teachers' self-efficacy and the impact on literacy achievement to determine how professional development (PD) positively impacted teachers with high self-efficacy. The study was conducted in a fringe-rural school district with fewer than 2,200 kindergarten through fifth-grade students. The first set of quantitative data was collected by administering the Teachers' Sense of Self-Efficacy Scale (TSES) from teachers with various levels of experience. The second set of data comprised Lexile scores and student growth percentile (SGP) scores from Renaissance Learning. Qualitative data were collected from initial focus groups and follow-up individual interviews to determine the traits and characteristics of PD opportunities that research participants found to be the most impactful on their pedagogical practices. To achieve this overall objective, the following research questions framed this mixed-methods study: 1. How do perceived levels of collective teacher efficacy affect kindergarten through fifth-grade student achievement in literacy comprehension skills as measured by Lexile scores reported by Star Early Literacy and Reading Assessments? 2. Is there a correlation between perceived collective kindergarten through fifth-grade teacher efficacy and kindergarten through fifth-grade student growth on Star Reading Assessments as measured by Star Enterprise scores? 3. What in-service professional development offerings, either self-selected or school district-provided, have kindergarten through fifth-grade teachers reported as having the greatest impact on their perceived efficacy for improving foundational literacy and comprehension skills of kindergarten through fifth-grade students? The findings of this study suggested that teachers, on average, feel well prepared for the classroom and thus have high efficacy. As the TSES measured teachers' understanding of student engagement, instructional strategies, and classroom management, research participants' average ratings fell within the quite a bit range on the scale's 9-point Likert scale. The research site's focus on literacy strategies at the time of the research study (2023) aided in their professional knowledge. Conversely, teachers with more teaching experience and graduate coursework reported, on average, lower efficacy, and reflect that they always have more to learn, noting why their efficacy scores are lower. When it comes to professional development, teachers noted that, overall, choice, relevance, and clarity is key. When teachers are able to take charge of their learning and select what they want that is in line with that they teach, are able to speak and breakdown the new ideas with colleagues, and the intention of the professional development is clearly explained as to how it will improve their pedagogy, teachers are more likely to utilize the new concepts in their professional work. Recommendations for educators include the suggestion of replicating the same study in the same or similar district in five years. As the research site is in the middle of implementing a few different initiatives, specifically a literacy initiative, and given Illinois' recent passing of a comprehensive literacy plan to guide literacy instruction across the state, all districts will be changing their literacy practices soon. Within a follow-up study, or when working to help improve teachers' perceived sense of self-efficacy, conducting observations to go along with the specific areas measured on the TSES would allow for personal reflection and growth for each educator, as well as perhaps some adjustments on future administrations of the survey. Finally, researching frameworks that help to measure effective implementation of an initiative would make the task easy for educational leaders to not only conduct but communicate to stakeholders. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]