The intended outcome of this qualitative study was to provide valuable information that could improve pre-service teacher education programs and inclusion professional development programs, as well as help guide school-based administrators on how to better support co-teaching at the secondary level. In order to accomplish the outcome, the purpose of the study was twofold: (1) to examine secondary co-teachers' perceptions toward their preparedness to co-teach in an inclusion classroom based on their pre-service training, overall professional development, and administrative support; and (2) to explore how well secondary co-teachers practice constructivist-oriented co-teaching. The research questions included: (1) How do secondary co-teachers perceive their preparedness to co-teach in an inclusion classroom based on their pre-service training, (2) How do secondary co-teachers perceive their preparedness to co-teach in an inclusion classroom based on their overall professional development, (3) How do secondary co-teachers perceive the administrators' role in supporting co-teaching, and (4) Based on secondary co-teachers' perceptions, how well do secondary co-teachers practice constructivist oriented co-teaching? The results from the study showed participants did not feel prepared to co-teach in an inclusion classroom based on their pre-service training or their professional development. The results also showed participants do not feel supported by their administrators and do not practice constructivist-oriented co-teaching adequately. [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.]