Research indicated that educators must consider socio-ecological accommodations because not all students learn in cooperative groups. Students must be taught how to discover the process of learning and to apply knowledge to real life situations. Gurian and Ballew (2003) identified differences in the male and female brain and the differences in how they learn. The single-sex grouping practice employed in this study allowed teachers an opportunity to teach students of the same sex. This study was designed to determine the effect single-sex classroom instruction has on African American males' achievement in ninth-grade mathematics compared to that of the other student groups. The researcher investigated a public school in a North Texas school district. The school's administration chose to offer alternative educational options for the students. Single-sex classrooms were created in the areas of mathematics and English Language Arts. Teachers taught single-sex classes of students from varied ethnic backgrounds during at least one double-blocked period each day. "Ex post facto" data were analyzed. An independent samples t-test and a two-way factorial Analysis of Variance (ANOVA) were utilized to test each hypothesis to determine whether significant differences existed in the scale scores of comparison groups on state-mandated assessments over a period of 3 years. The instrument used to measure academic achievement is the Texas Assessment of Knowledge and Skills. This study found that the mathematics scores of African American males in single-sex classes did not significantly differ from the scores of African American males in coeducational classes. The scores for the males in single-sex classes were slightly higher than that of males in coeducational classes at each grade level throughout the 3-year period. The mathematics scores of African American females in single-sex learning environments were not significantly different than those of African American males in single-sex classes. The scores for the female students were consistently higher throughout the 3-year period. This study identified the need for additional school choice options for students as a means of eliminating the achievement gap. [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.]