This qualitative case study explored the methods of how one Mid-Atlantic suburban school district implemented the inclusive practice of co-teaching at the secondary level to examine its effectiveness. Two high schools were evaluated through interviews with co-teachers who implemented this inclusive practice and administrators who supervised and evaluated them. Participants included six co-teaching dyads and three administrators who were responsible for supervising and observing specific dyads. Co-teachers' perspectives and insights were conveyed through interviews that shared their experiences, best practices and administrative support. Supervising administrators shared how they supported and evaluated their dyads through interviews. Analyses supported a need for ongoing professional development to aid co-teachers' collaborative efforts and revealed best practice that could help create a comparable framework to share the roles and responsibilities more equitably to build interdependent relationships. Analyses from this research study revealed that administrators needed professional development to provide effective guidance, support and feedback for their co-teaching dyads as they collaboratively co-instructed using the various models of co-teaching. [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.]