This research study examined the impact of one particular standards-based set of high school mathematics curriculum materials, Contemporary Mathematics in Context, on the achievement of African Americans in high school mathematics. The conceptual framework for the research study builds on the curriculum model of the Third International Mathematics and Science Study (TIMSS) researchers, the research framework of the Center for the Study of Mathematics Curriculum researchers and the research of Johansson. The conceptual framework includes five areas of curriculum--the intended curriculum, the assessed curriculum, the learned curriculum, the implemented curriculum and the potentially implemented curriculum. The research study focused on the role of the textbook in influencing the mathematics achievement of African American students in high school mathematics and compared the achievement scores and achievement levels in Algebra 1 and Algebra 2 of students who were taught using standards-based curriculum materials for high school mathematics to the scores of students who were taught using conventional curriculum materials for high school mathematics. Results indicated that the standards-based curriculum materials made a significant positive difference in Algebra 1 achievement scores and levels for African American students. Results indicated that the standards-based curriculum materials did not make a significant positive difference in Algebra 2 achievement scores for African American students. In both Algebra 1 and Algebra 2 results, the difference in the achievement scores of African American and other students were smaller for students using the standards-based curriculum materials than for students using conventional curriculum materials. Although the textbook is not the only factor that matters in learning mathematics, this study indicates that the choice of textbook can make an important difference in the achievement of African Americans in high school mathematics.