The current study was undertaken as an effort to attend to the potential giftedness of economically disadvantaged students, to give opportunities for mathematics acceleration, and to provide a sequential, individualized mathematics program for students of high mobility. The authors evaluated the Project SAIL (Students' Active Interdisciplinary Learning), a Javits program that sought to develop the latent mathematics abilities of economically disadvantaged students through the use of a highly sequential, individualized mathematics program that allowed for acceleration. Results showed that an individualized supplemental mathematics program, such as Kumon mathematics, enhanced mathematics abilities in economically disadvantaged students. The purpose of this study was to measure the effect of the Kumon mathematics program on the mathematics performance of students involved, to allow students to move or accelerate at their own pace, and to measure the retention level of the mathematic skills acquired by the student participants. This evaluation study provides some evidence of the efficacy of Kumon in improving the mathematics skills of economically disadvantaged students. The study also demonstrates the success of Kumon in strengthening the mathematics retention levels of students.