While some African American students perform as well as or better than their White peers on standardized tests, African Americans as a group attain lower scores on standardized tests than their White peers. This phenomenon has been addressed extensively in educational research. However, not much empirical research has been conducted to investigate whether a complementary assessment, such as the clinical interview, would provide more information about African American students' mathematical knowledge than a standardized test. Qualitative clinical interview methodology was used to explore the performance of the student participants on the clinical interviews and on the standardized test as well as teacher feedback about these students' mathematical knowledge. Data were gathered from three main sources: clinical interviews, standardized test results, and teacher interviews. Data were coded to identify common themes that shed light on the research questions. Most of the students performed better on specific items from the standardized assessment, the New Jersey Proficiency Assessment of State Standards (NJPASS), than on the clinical interview items. The scores on both assessments revealed much disparity among participants' mathematical competencies. The clinical interviews affirmed or changed the teachers' opinions of their students. The information from the clinical interviews fostered discussion of pedagogical practices. [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.]