Coteaching strategies have been implemented in many of the inclusion math classrooms in an attempt to improve the achievement of students. Math achievement continues to be a concern as reported by the National Mathematics Advisory Council in 2007. Educators and previous research reported that coteaching does not improve student achievement. The purpose of this study and the research question was designed to investigate, determine, and examine if coteaching has an impact on regular education students' achievement on an algebra assessment in the eighth grade. This concurrent mixed methods design used test data from a convenience sample of 70 eighth grade students and 6 math coteachers from a small rural middle school in a southern U.S state. The students were divided into a cotaught class (experimental) and a noncotaught class (control group). The teachers' perception and implementation of the coteaching model within the inclusive classroom was determined through interviews using a semi-structured interview guide. Students' achievement was measured based on math scores on a Basic Skills Algebra Assessment given at the beginning and end of 12 weeks. A two-way analysis of variance (ANOVA) was conducted to assess if differences exist on algebra achievement scores by group (control vs. treatment) and time (pretest vs. posttest). The results of the post hoc analysis, consisting of two independent sample t tests and two dependent sample t tests, revealed that significant mean differences did in fact exist on algebra achievement scores for only the experimental group suggesting that scores increased from pre to posttest. The interview data indicated that the teachers' perception of student learning was greater in the cotaught classroom. Evidence is provided to coteachers and administrators in support of implementing the coteaching model. It supports a change in students' attitudes and perceptions of other's differences as well as their ability to learn mathematics. [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.]