A school perimeter security system includes a registry database. The registry database includes: registered student mobile device identifiers, registered non-student mobile device identifiers, and a matching of students with authorized non-students with whom the students are permitted to be paired with near the perimeter. At least three beacon devices are located within the school perimeter, positioned to establish a boundary area near the perimeter, detect and establish communication with mobile devices entering the boundary area, obtain an identifier from each mobile device that enters the boundary area, and facilitate trilateration of all mobile devices within the boundary area. The processor and beacon devices cooperatively interact to identify every mobile device entering the boundary area, track the location of every mobile device within the boundary area, compare the identified mobile devices with identifiers in the registry database and, transmit an alert notice when a condition is satisfied.