A goal of the No Child Left Behind (NCLB) legislation is to improve educational opportunities for disadvantaged students. Schools that have not made adequate yearly progress (AYP) for 2 or more years are identified as schools in need of improvement and are therefore required to provide supplemental education services to students. The problem addressed in this study was low achievement scores in a suburban school district in the Southeast resulting in an increasing number of schools failing to meet AYP. The theoretical foundation of this study was framed in John Carroll's learning model and Benjamin Bloom's mastery learning approach (MLA). The research questions focused on determining whether participation in a supplemental program had an effect on student achievement in reading and math; additionally, differences in student achievement between ethnic and gender groups were investigated. Archived pretest and posttest data were analyzed using a paired-samples t test to measure the degree to which the supplemental program affected student achievement. Findings indicated a statistically significant improvement for overall reading and math achievement (p = 0.000 for df = 86 and df = 93, respectively, tested at p < 0.001) and no significant difference in achievement between ethnic and gender subgroups. This study could lead to positive social change by providing sufficient evidence to local education authorities to reevaluate instructional strategies for low performing students. If access to extra educational resources can increase the reading and math achievement level of low-income students, these students may be more successful in the regular classroom. [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.]