The problem addressed in this study was that teachers struggle to apply the middle school concept in three middle schools in the U.S. region of New England. This study was a qualitative investigation of teachers' perceptions of the middle school concept and their needs for additional support to effectively apply it. The conceptual framework for this study was the middle school concept itself, which theorizes five essential attributes of effective middle schools: responsive, challenging, empowering, equitable, and engaging. The research questions were about teachers' perceptions of their knowledge about and application of the middle school concept, the extent to which the middle school concept is being applied, and the recommendations regarding the professional development and support needed for applying the middle school concept. Face-to-face, semi-structured interviews were conducted with 15 teachers from three middle schools in the target district. Data analysis involved open and axial coding and thematic analysis. Five main themes emerged from the study, indicating that participants recognized the unique developmental needs of middle school students, emphasizing the importance of teaming, and revealing that successful implementation of the middle school concept requires addressing teacher resistance, navigating school policies and practices, and providing robust leadership and ongoing professional development. This study may contribute to positive social change by helping policymakers, educators, and administrators better understand teachers' perceptions of the middle school concept, ultimately aiming to improve middle level education. [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.]