The concepts and ideas of mathematics is a major element of educational curriculum. Many different instructional strategies are implemented in mathematics classrooms. The purpose of this study was to evaluate the effect of an instructional model utilizing hands-on learning and use of manipulatives on mathematics achievement of middle school students. A quasi-experimental non-equivalent control-group design was used to examine 145, seventh-grade students from a North Georgia middle school. Data was collected to analyze if changes were experienced in pretest/posttest scores. A Mann-Whitney test was run and revealed initial group differences between the whole control and whole experimental groups, and also between average-achieving control participants and average-achieving experimental participants. An ANCOVA was then run to analyze the null hypotheses for the first and third research questions, revealing that there was no significant difference between posttest scores of the control and experimental groups when compared as whole groups. In addition, no significant differences were found between posttest scores of average-achieving participants in the control and experimental groups. Individual Mann-Whitney tests were used to examine the second and fourth research questions. The results showed that there were no significant differences between two of the subgroups (low-achieving control versus low-achieving experimental, high-achieving control versus high-achieving experimental) of the control and experimental groups. [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.]