This causal-comparative study provides a descriptive analysis of the impact of participation in co-taught classrooms compared to traditional classrooms on the academic growth of students with and without disabilities. This issue is examined in English language arts and mathematics using the New York State testing program results. A quasi-experimental design and a post hoc statistical analyses using t-tests was used to look for statistical differences between identified groups. Achievement growth was operationalized as the student growth percentile on the NYS New York State assessments, and group means were compared by grade level over five years. The findings from this study suggest that achievement in English language arts and mathematics for all students in integrated co-taught classrooms is likely to be comparable to, or better than, that for students in traditional classrooms. Further, participation in a co-taught classroom is unlikely to impact nonidentified peers negatively and may benefit them, particularly in mathematics. Additionally, students with disabilities may benefit slightly more from a co-taught setting than their peers not identified with disabilities. Considerations for policymakers and administration are discussed as well as recommendations for further research. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]