Current educational policies that have articulated from IDEA are driving the adoption of inclusionary practices in schools. These policies present challenges to general education, secondary education, and dual-licensed teachers at the secondary level. Secondary general education teachers may lack the pedagogical knowledge necessary to accommodate for students with special needs; special education teachers may lack the competence in content to ensure students with special needs are mastering the required standards. Co-teaching partnerships allow students to be educated in an environment that includes teacher expertise in both areas--a general educator for content-specific instruction and a special educator for data collection and accommodation expertise. This quantitative survey research explored the impact that co-teaching has on teacher efficacy within the co-taught classroom and the stand-alone classroom for general education teachers, special education teachers, and dual-licensed teachers at the secondary level. Quantitative statistics were used to determine if co-teaching impacted teacher efficacy in the constructs of student engagement, instructional strategies, and classroom management. When a repeated-measures t-test for non-independent samples was conducted, the study found that there was a significant difference in teacher efficacy between the stand-alone classroom and the co-taught classroom in the constructs of student engagement, instructional strategies, and classroom management for general education teachers and teachers who are dual-licensed. While efficacy is higher in the co-taught classroom than in the stand-alone classroom for teachers with a special education license, a significant difference did not exist. [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.]