The purpose of this qualitative multiple case study was to examine how the interorganizational relationship between school administrators and law enforcement personnel with diverse cultures, missions, and objectives collaborates to create, implement, and sustain emergency management readiness. The theoretical concept that guided this study involved interorganizational theories as they relate to two or more organizations working together toward a common goal. This study used purposeful sampling of 12 participants from three school districts from the states of Alabama, New Mexico, and Illinois. Interviews, documents, and artifacts, such as school safety plans, school safety drills, safety audits, and Safe School rubrics, were analyzed as part of the data collection process. Results indicated that the creation of emergency management plans is primarily the work of district administrators. The implementation process included district administrators and building principals with minimal input of law enforcement personnel. However, the process of sustaining school emergency plans is a joint effort between school and law enforcement personnel. Analysis of data affirmed the importance of having an effective interorganizational relationship between school and law enforcement personnel in the context of school safety to create an effective emergency management plan in the school.