The purpose of this research is to determine the requirements of being a school principal and investigate the pre-service trainings of primary and middle school principals in the United States. In accordance with this aim, semi-structured interviews were conducted with 16 primary and middle school principals from the state of Michigan. In this research, the NVivo 8 software program was used for qualitative analysis, while the data from the interviews were analyzed through induction analysis. The results indicated that all of the school principals identified two fundamental requirements of being a principal: (1) a master’s degree in educational administration and (2) administration certification. Furthermore, it was emphasized that if any principal candidates possessed master’s degrees in disciplines other than educational administration, then they were required to participate in the “+18” program (provided by various educational administration programs at state universities) and acquire all 18 credits that consist of fundamental courses in this field of study. In terms of pre-service education, the school principals stated that the most important pre-service trainings in the process of their professional development included internships and courses taken during their graduate study.