The Advanced Law Enforcement Rapid Response Training (ALERRT) Center at Texas State University has released new research in partnership with the Security Industry Association (SIA) examining how locked doors and access control measures affect the outcomes of active shooter incidents in U.S. schools.

The report, “The Role of Locked Doors and Access Control in School-Based Active Shooter Events” analyzed 54 school-based active shooter incidents from 2000 to 2025 that resulted in 324 total victims. Researchers reviewed factors including attacker profiles, movement through schools, weapons used, timing of attacks and whether doors were locked or unlocked. 

“The most common way an attacker entered a space was not by defeating a lock — it was by walking through a door that should have been locked but wasn’t,” said Hunter Martaindale, Ph.D., director of research at the ALERRT Center and lead researcher on the report. “Nearly two-thirds of the doors in our dataset were unlocked or propped open at the moment of attack. The hardware only protects students, teachers and staff when it is consistently used. The available data give empirical weight to a recommendation the field has long made on principle: lock the door.”

The findings point to how basic physical security measures and procedural compliance can significantly affect casualty outcomes during school-based active shooter incidents.

Among the report’s most significant findings:

• 69% of successful perpetrator entries were through an unsecured door, as nearly two-thirds (61.7%) of doors involved in incidents were found unlocked or intentionally propped open.
• Over half (55.6%) of the shooting incidents occurred in high schools, compared with elementary schools (18.5%) and middle schools (16.7%).
• More than three-quarters (75.9%) of incidents involved a lockdown procedure, but in some cases lockdowns were not initiated until after the attacks had effectively concluded.
• The profiles of the attackers varied greatly depending on the type of school. In high school and middle school shooting incidents, most attacks were carried out by insiders (88.9% of shooters in middle schools and 83.3% of shooters in high schools were current students). In elementary school incidents, however, none of the perpetrators were current students — all were outsiders.
• Nearly 50% of attacks were initiated in hallways (24.1%) and outside areas (24.1%).
• In active shooter incidents in schools, casualty likelihood was three times higher when doors were unsecured, compared to secured doors.
• No functioning locked door in the data set was successfully breached through defeating the locking mechanism.

Threat profiles differ by school level. Current students accounted for 83.3% of high school perpetrators and 88.9% of middle school perpetrators, and in these settings exterior doors did not function as a barrier to entry. None of the ten elementary school perpetrators were current students; each gained access from outside the building, making the exterior door the primary point at which access could be denied or delayed. These patterns indicate that effective door-security strategy priorities, while overlapping, can differ by facility type: exterior perimeter integrity and controlled visitor access are most consequential at elementary schools, while rapid interior lockdown capability is most consequential at secondary schools.

Glass is the primary point of mechanical failure. Nine mechanical breach attempts were documented across the 54 events, of which six were successful. In every successful breach, the perpetrator defeated the barrier by shooting through glass; no locking mechanism in the dataset was defeated mechanically. Four of the six successful breaches involved aluminum-frame exterior doors with glass panels.

Flush doors with functional locks were never successfully breached. Compliance, not hardware, is the most common failure mode. Among 47 doors with known status, 29 (61.7%) were unlocked or propped open at the time of the attack. The most common way a perpetrator gained access to a space was not by defeating a lock, but by passing through an unsecured door. The Uvalde case study illustrates how routine noncompliance with locking policies, together with unrepaired hardware defects, can render existing security infrastructure ineffective.

Speed of lockdown shapes outcomes. The Evergreen High School incident demonstrates the protective value of rapid response: staff initiated a lockdown 42 seconds after the first shot, and the attacker subsequently spent nearly three minutes unsuccessfully attempting to re-enter the building before abandoning the effort. Across the broader dataset, 75.9% of incidents involved some form of lockdown, but the timing of initiation varied widely. Locking hardware that can be engaged quickly from inside the room, integrated alert systems, and staff empowered to initiate lockdowns without awaiting administrative confirmation each contribute to shorter threat-to-secure intervals.

The report also examined the 2022 shooting at Robb Elementary School in Uvalde, Texas and the 2025 shooting at Evergreen High School in Evergreen, Colo. as case studies to evaluate how physical security measures and procedural compliance influenced outcomes.

Researchers shared eight evidence-based policy recommendations for school administrators, security professionals and policymakers. Focus areas include:

• The foundational importance of every classroom door having a functional lock that can be engaged from inside the room
• The vulnerability of common areas such as hallways, cafeterias, gyms and courtyards
• The role of maintenance and repairs as essential security functions
• The measurable impact of school security culture and procedural compliance on outcomes
• The importance of protecting glass features in and around doors
• Strong concerns regarding aftermarket additions like magnets and door barricade devices, which the report found add unnecessary complexity and serious hazards

The independent research was supported through a grant from the SIA Endowment Program. According to SIA, the findings are intended to help school administrators, educators, security professionals, law enforcement agencies and policymakers evaluate school safety practices and guide future security investments.

The findings were discussed during a June 18 webinar hosted by SIA and the ALERRT Center featuring Dr. Martaindale.