Economically disadvantaged students are being outperformed by their non-disadvantaged peers in middle school mathematics. This problem is evidenced by 2013 data from a national middle school mathematics assessment which revealed an achievement gap of 27 scale score points. Closing this gap is important to schools with high populations of economically disadvantaged students. To that end, the purpose of the study was to measure the impact of Kagan Cooperative Learning model on North Carolina End of Grade (NCEOG) mathematics achievement scores of 238 economically disadvantaged students who were administered the NCEOG in 2011 and 2012. The theoretical foundations of this study were found in cooperative learning, specifically Kagan. One research question was asked to determine the extent to which Kagan is effective in raising economically disadvantaged students' achievement levels. A quasi-experimental design was used to examine the pretest and posttest scores of the sample. The sample of 238 students consisted of 124 students in the control group and 114 students in the treatment group. ANCOVA was used to analyze the data and revealed a statistically significant difference between scores from the control group and the treatment group. These findings support the use of Kagan to raise achievement levels of economically disadvantaged students in the area of middle school mathematics. Positive social change can occur as teachers use Kagan to create opportunities for students to engage in the learning process through cooperation. As this learning approach becomes the norm and the climate of the classroom changes, students learn to communicate mathematical thinking. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]