The purpose of this quantitative comparative descriptive study was to analyze the effect of an after school program on high school at-risk students' English/language arts and mathematics achievement on state standardized tests. This investigation examined the effects of out-of-school time support, specifically a nationwide after school program, 21st Century Community Learning Centers After School Programs (21st CCLC), and its effect on at-risk youth who were often challenged by external factors, which prohibited some from academic success. A quantitative comparative descriptive design was used. The theoretical framework that served as a foundation for this study was embedded in the logic model. This model supported the implementation of the 21st CCLC and its effect on student academic performance as measured by Maryland's high school state exit examinations. Through the use of independent samples t-tests, the null hypotheses were tested. Based on exit examination results from the school year, 2010-2011, there was a statistical significant difference between the mean Maryland High School Assessment (HSA) test scores of tenth grade students who participated in an after school program and those who did not participate in an after school program. This quantitative study analyzed the data results of at-risk students' performance on Maryland's high school state examination and discussed the implications the 21st CCLC had on the success rate of at-risk participants and non-participants of this program. English/language arts and mathematics HSA outcomes of at-risk students who did not participate in the 21st CCLC were significant, <0.05. A statistical significance was noticed between participants of the 21st CCLC and non-participants as identified on the Maryland state HSA in 2011. [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.]