Preventing negative perceptions towards co-teaching among co-teachers is essential to overcoming barriers in today's inclusive school environments. In the ideal co-taught classroom, both the general education teacher and special education teacher work collaboratively to ensure special needs students have the same access to the general curriculum alongside their non-disabled peers. Unfortunately, negative co-teaching perceptions and practices are destroying effective collaboration in today's schools. The problem addressed by this study was that special needs students are receiving a less promising education as a result of existing inadequate co-teaching perceptions and practices in today's public schools. The purpose of this qualitative case study was to explore perceived barriers to effective co-teaching to determine factors that preclude secondary co-teachers from effectively implementing best practices in the co-teaching environment of a suburban public school located in northwest Virginia. A qualitative approach allowed the researcher to investigate participant co-teaching teams' lived experiences to better understand perceived factors that preclude co-teachers from effectively implementing best practices in the collaborative environment. Social constructivism was used as the guiding theoretical framework for this study. This study was conducted during a nine-week period and included individual initial, mid interviews, and focus group discussions that were conducted with two Math and English co-teacher teams who worked with students from seventh through eighth grade. As a second method of data collection, all participants also completed the Perceptions of Co-teaching Survey (PCTS) to further corroborate information from the interviews. Data from interviews, focus groups, and the PCTS were analyzed manually by the researcher for patterns, themes, and categories. The researcher also provided a content analysis of the current academic literature to provide solutions to participant's perceived barriers towards implementing co-teaching best practices. This study revealed that co-teacher held perceptions towards co-teaching best practices and barriers to those practices were shaped through their individual lived experiences in the co-taught classroom. It was concluded that factors, both perceived and real, exist that preclude secondary teachers from effectively implementing best practices in the co-teaching environment. Broadening the knowledge of co-teacher held perceptions towards co-teaching barriers may help educators improve the perceived factors of co-teachers that they believe preclude them from effectively implementing best practices in the co-teaching environment. [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.]