The efficacy of supplemental instruction was investigated in this study. The problem addressed by this study is the lack of course completion and persistence for at-risk community college students The purpose of this quantitative quasi-experimental study, which was informed by the student integration and student involvement theories espoused by Tinto and Astin, was to examine the effect of an academic support program, supplemental instruction, on the final course grade and persistence to the subsequent semester of at-risk students in college level gatekeeper courses at a small southeastern Texas college. This study addressed two research questions (1) What, if any, difference exists in final course grades in gatekeeper courses for at-risk students who participate in supplemental instruction and those who do not participate in supplemental instruction, and (2) What, if any, difference exists in persistence to the subsequent semester for at-risk students who participate in supplemental instruction and those who do not participate in supplemental instruction? The study population was at-risk two-year college students enrolled in gatekeeper courses. Most data was collected at the end of the fall 2017 and fall 2018 semesters and included final course grades, attendance in supplemental instruction, age, gender, race, college status, and socioeconomic status. Persistence data was collected on the twelfth class day in the subsequent semesters. The results from data analysis demonstrated there was no statistically significant difference in final course grades or persistence between the treatment and control groups. By investigating the effect of supplemental instruction in two-year colleges, higher education leaders have additional information on which to make decisions about continuing supplemental instruction programs. While the findings of this study were not consistent with current literature, it highlights the need for additional quantitative studies in two-year colleges with larger student populations. [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.]