There is a consequential amount of research in regards to coteaching and student achievement in students with disabilities. Although there is a substantial body of research, there is still uncertainty whether achievement in mathematics differs between students with and without disabilities in cotaught and non-cotaught classrooms. Therefore, the purpose of this quantitative, casual-comparative study was to examine what, if any difference exist in the overall student achievement in math between groups of special education students and general education students in cotaught and non-cotaught mathematics classes. Participants included 186 seventh grade students at a middle school in Southeastern United States. Archival data were collected from 2014-2015 Star Math Scores and were analyzed for statistical significance across groups of special education and general education students using two-way ANCOVA. Results indicated there were no significant differences in achievement scores between students with SLD and general education students in cotaught classes together, no significant differences between students with SLD in cotaught and general education students not in cotaught classes, no significant differences between, no significant differences between students with SLD in resource classes and general education students in cotaught classes, no significant differences between students with SLD in cotaught classes and SLD students in resource classes, and no significant differences between students with SLD in cotaught classes and general education students in general education classes. However, there were significant differences in achievement scores between students with SLD in resource classes and general education students in non-cotaught classes. The findings of this study have the potential to influence school administration and district leaders to incorporate professional development opportunities and training for teachers. The study results also have the potential to impact the values, attitudes, and development of general education and special education classrooms by substantiating dissimilarities in academic achievement based on coteaching and non-coteaching. Recommendations for future research include examining coteaching in elementary and secondary school settings in multiple school districts. Another recommendation is to examine coteaching in mathematics to include six and eighth grade students. Future research could replicate the current study, but examining student achievement in cotaught classes and include years of teaching experience and teacher certification as variables. [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.]