This phenomenological qualitative research study aimed at understanding the scheduling practices of middle school principals in the Commonwealth of Pennsylvania. More specifically, this study examined how frequent changes are made to the middle school master schedule, factors that contribute to scheduling changes, barriers to scheduling, and the scheduling model middle school principals believe best serves students at the middle level. Survey data was collected from 40 middle school principals across the Commonwealth of Pennsylvania from schools representing diverse communities, student populations, varied principal experience, and varying scheduling input. Criterion sampling was used to select 8 middle school principals for a more in-depth semi-structured interview to garner a better understanding of their combined lived experience with master scheduling. Participants were selected based on years of services as a middle school principal, type of community, school socioeconomic status, and student enrollment. The significant findings of this study include: middle school principals have adapted schedules to accommodate student needs, local policies do not have an impact on master scheduling, collective bargaining agreements and staffing do have an impact on master scheduling practices, data impacts master scheduling, and budgets are a barrier to master scheduling. This study indicates block scheduling is the preferred model of middle school principals, middle school principals consider the master schedule as the foundation of the school, middle school principals change the master schedule to accommodate student needs, and there are factors that impact the master scheduling practices of middle school principals. [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.]