An achievement gap exists in mathematics between low-income African American male students and their European American counterparts. Although this problem has been approached using different interventions with minimal results, the impact of homogenous grouping is not well understood in spite of its use. As a result, this study was conducted to investigate if the classroom setting had an effect of the test scores of 9th grade African American male students. Bandura's social-cognitive learning theory was the theoretical framework. The purpose of this ex post facto, posttest-only study was to test the effect of single-gender classes on the academic performance of low-income African American male students in mathematics. The test scores of 111 African American male students were analyzed using a one-way analysis of variance to determine if classroom setting (single gender and coeducational) had an impact on students' achievement in 9th grade mathematics. However, there were no statistically significant differences in math scores. The lack of significant results indicates that more research is needed in order to determine the value of single-gender education for 9th grade African American students. Recommendations for further study include examining the performance of female students and incorporating an intervention of professional development for teachers of single-gender classes. Given that many other reform attempts have had little to no impact on decreasing the achievement gap for African American male students, single-gender classes may yet prove to be an inexpensive, yet effective means of providing a positive, nurturing academic environment for African American male students. [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.]