The purpose of this quasi-experimental, quantitative study was to investigate the effectiveness of supplemental instruction (SI) as a means to address the existing high attrition and low graduation rates evidenced at a rural southern community college. The research problem addressed the high attrition rates in barrier courses and low graduation rates evidenced at the community college. Students unable to successfully complete barrier courses often alter their educational goals or eventually drop out. Following the constructivism and social constructivism theories, which state that learning is shaped by social interaction, the research questions examined the impact of SI on GPA, graduation rates, and persistence in identified barrier courses. Additional subgroup comparisons between adult learners and traditional students participating in SI were completed. A convenience sample of 70 students currently enrolled in barrier courses was used. Independent samples t tests were conducted and found no significant differences in grades, GPA, or graduation rates for those participating in SI versus those who did not. Independent samples t tests also revealed no significant differences between graduation rates and GPA of adult students versus traditional students participating in SI. Based on the data, the SI model was found to be minimally effective. These findings, along with recommendations to complete a formal, summative evaluation and incorporate professional development training, were presented in the culminating project, a white paper. This study may contribute to social change by helping decision makers properly assess the value of SI to both traditional and nontraditional students, benefiting all who attended the studied site, as well as indirectly impacting the community. [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/en-US/products/dissertations/individuals.shtml.]