Doors serve a variety of needs and purposes in schools: (1) Exterior doors provide building security and protection from the elements; and (2) Interior doors control the movement of people among school spaces, help control noise and air flow, and act as flame and smoke barriers during a fire. In a lockdown, they serve as safety barriers. From a security perspective, the most important function of a door is to control entry. Entry control involves the configuration, strength, durability, and composition of the door, its hinges and its frame, and the control and effectiveness of its latching and locking hardware. This paper explains the building and fire code requirements governing doors in schools, discusses existing door locking options, and describes the varied and sometimes conflicting safety- and security-related functions of school doors. It also includes the California Department of Education's recommendations for school entrances, doors, and access control. (Contains 8 endnotes.)