The study was designed to address how teachers' self-efficacy influenced student achievement through the use of a formative assessments in the classroom. Student achievement and learning outcomes are the primary focus for educators, and the constant quest to improve student learning is a common theme. The problem addressed was low levels of teacher efficacy and years of teaching experience may be linked to and negatively impact student achievement scores, resulting in lowered levels of preparedness for college readiness. The purpose of this quantitative correlation research study was to examine the relationship among the predictor variables of teachers' efficacy and teachers' years of experience to the outcome variable of student achievement in reading and mathematics in a diverse school district in South Carolina. The conceptual framework for the research was based on the effectiveness of formative assessments to advance student learning using the research of Bloom, Guskey, and Black and Wiliam. Participants completed the Teacher Self-Efficacy Scale to measure teachers' sense of efficacy and student achievement scores using the STAR formative assessment. The results from the teacher survey, including years of experience, and the teacher's STAR results were compared using the correlational design using a Pearsons correlation and regression model. The results indicated positive correlations for both teacher-efficacy levels and the content areas of English and language arts (ELA) and mathematics. A significant correlation existed between student achievement ELA scores and teacher self-efficacy levels. There was no correlation between the years of experience and student achievement scores. The results indicate teacher-efficacy levels affect teaching in the classroom and impact students gaining greater learning and achievement. Recommendations would include learning more about teacher efficacy and intentionally seeking ways to increase teacher efficacy levels to positively impact and increase student learning. [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.]