Rethinking Campus Security From the Inside

• By Mitzi Amon
• November 17, 2025

For decades, campus security strategies focused on keeping threats outside school walls. But since the tragedy at Columbine High School, data has shown that many attacks begin inside the building, often in classrooms and corridors. This shift has prompted schools to rethink security from the inside and place greater emphasis on interior elements such as classroom doors. This shift is evidenced by a new generation of classroom door systems engineered to delay inside intruders and an ASTM standard that raises the bar on how these systems must be designed to defend against attack.  

Classroom Door Security, Then and Now
Before 1999, classroom doors were simple wood panels with basic hardware meant to protect property and control access. The Columbine tragedy and subsequent shootings such as Virginia Tech and Sandy Hook Elementary School redefined that function, transforming the classroom door into a potential life-safety barrier. The growing number of school shootings also underscored the need for a broader definition of campus security.  

In 2014, the Partner Alliance for School Safety (PASS), a coalition of education, public safety, and industry experts, united to develop a layered and tiered approach to securing the school environment. In 2015, PASS released its first “Safety and Security Guidelines for K-12 Schools.”

The guidelines, now in their seventh edition, define five layers of protection that begin broadly with District-Wide and Digital Infrastructure layers and work inward to the Campus Exterior Perimeter, Building Perimeter, and Classroom Interior. Topping the list of architectural features in the Classroom Interior layer is door construction. The PASS guidelines were the first to recommend classroom and corridor doors be a minimum of 1 ¾-inch thick, constructed of solid-core wood or heavy-duty steel, and installed in a steel frame. It also recommends doors that separate interior areas be rated to ASTM F3561, the Standard Test Method for Forced-Entry-Resistance of Fenestration Systems After Simulated Active Shooter Attack.  

Introduced in 2022, ASTM F3561 is the first test standard to assess the full door assembly, which includes the door panel, frame, glazing, lock, strikes, and hinges. Before ASTM F3561, door manufacturers relied on the Shooter Attack Test Method (FTD-SA) to evaluate performance. FTD-SA applies a combination of ballistic and forced-entry testing and assigns a security level to the tested product, but it does not provide certification.

ASTM F3561 is patterned after FTD-SA, using similar ballistic and forced-entry scenarios and security levels, ranging from Level 1 to Level 8. What’s different is the ASTM standard formalizes the testing protocol and provides certification, allowing security component specifiers to compare ASTM-certified door systems from different manufacturers on equal terms.  

For school safety and security professionals involved in constructing, renovating, or retrofitting classrooms and corridors with doors that meet modern security standards, ASTM F3561 and FTD-SA labels are the best industry indicators of rigorously tested performance.

Since ASTM F3561 is only a few years old, leading door manufacturers offer a range of security levels that include both ASTM-certified and FTD-SA-tested options as they work toward testing more models to the new standard. Some manufacturers have also implemented user-friendly security tier language, like ASTM certified, FTD-SA tested, and security enhanced, to make it easier for schools to identify which doors best match their needs.  

In addition to attack-resistance, ASTM-certified door systems are capable of addressing a variety of other, more practical school needs. These include meeting ADA compliance and fire ratings as well as delivering classroom comfort with sound attenuation for quieter spaces. Systems can be further customized for door size, glass and glazing features (including no glass), door surface finishes such as wood veneer, high-pressure decorative laminate, and paint, and core materials. ASTM certification can be specified for door pairs too, providing added security in spaces such as corridors, libraries, cafeterias, and gymnasiums.  

Working with a knowledgeable manufacturer is essential for navigating the complexities of modern safety standards such as ASTM F3561. Manufacturer expertise can guide schools in selecting door system features that offer the best balance of security, functionality, and cost and can assist decision-makers with local building code and fire code compliance, ADA requirements, and district specifications.  

A New Standard for Classroom Door Protection
The first classroom door on the market certified to ASTM F3561 standard was Forte Opening Solutions’ Aspiro® Series Defendr Door System™. The system combines a solid-core door of structural composite lumber or heavy-duty particleboard, ANSI/BHMA Grade 1 hardware, a 14- or 16-gauge steel frame, and laminated attack-resistant glazing in an 18-gauge metal vision frame. The term system in the product name is intentional. Unlike classroom doors of the past for which individual components stood alone as their own measures of security, the ASTM security standard requires all components to work together to withstand dual-phase attacks.  

For example, during the ASTM ballistic assault phase, the tester fires ten rounds from an AR-15 rifle into the door glazing and five rounds into the lock hardware to replicate how an attacker might attempt to breach the door.

When ballistic entry fails, intruders may make a second attempt using brute force to gain entry. To simulate this type of attack, testers use an impactor dropped from a height to deliver 400-ft-lbs of energy. Impacts are repeated at 50-ft-lb increments until the door system fails. To pass an ASTM level, the system must sustain two sequential impacts at the same level of force without being compromised.   

Before choosing an ASTM-certified door and corresponding security level, schools should first conduct a threat assessment and balance the threat level with their available budget. It is important to note that the highest security levels are also the most costly, and they may not accurately reflect a school’s needs in terms of threat protection.

Also, professionals responsible for updating classroom door security in older buildings should be cautious about opting for much less costly glazing-only solutions. Products like window security film can help delay entry, but they do not provide protection comparable to an ASTM-certified door system. Security film also comes with additional risks associated with improper installation.  

Securing the Future
From simple wooden panels to integrated, attack-resistant systems, classroom doors have become a crucial line of defense in modern school safety. What was once a passive architectural feature is now a tested and certified security component designed to withstand threats that once left schools vulnerable. With clear performance benchmarks like ASTM F3561 and innovations in door system design, schools can create environments that are both secure and supportive—places where teachers can teach, students can learn, and safety can stand guard in the background.