National and international assessments indicate that U.S. students lose ground in mathematics as they progress into middle and high school. It is suggested that the organization of traditional mathematics textbooks, which form the backbone of mathematics instruction, hinders acquisition of the foundational skills necessary for success in higher mathematics, thereby leading to low math performance. Traditional mathematics textbooks are organized into a spiral design where many topics are covered, but none are covered in depth. An alternative to the spiral organization, which is unique to Direct Instruction programs, is the strand design. Textbooks organized around a strand design focus on a relatively small number of topics over a long period of time. As topics are mastered, they are integrated into new strands that represent increasingly complex mathematical concepts. This article examines the disadvantages of the spiral design and shows how organizing textbooks into strands can increase the effectiveness of mathematics curricula. (Contains 2 figures.)