Barricading also has detractors. Oxford teachers used a product called a Nightlock, a barrier at the bottom of doors, and some students said they blocked them with furniture. But evidence from past school shootings suggests that barricading can increase noise and indicate to gunmen where people are hiding, Mr. Dorn said.
The most important strategies for students and teachers to use in the event of an active shooter are locking doors, turning off lights, hiding out of sight lines and ignoring any door knocks or questions from outside of a room, said Jaclyn Schildkraut, a professor of criminal justice at the State University of New York at Oswego, who studies school lockdown drills.
But the bigger questions about the active shooter drills go beyond tactics — and spill over into how schools should balance the threat of violence with the mental health of students.
Dr. Schildkraut’s research has suggested that even a relatively gentle lockdown drill can “slightly” decrease students’ sense of safety at school, she said. But she argued that the drills were necessary because adolescents who participated in them reported “feeling more prepared and more empowered,” she said. “It is better to have it and not need it, then need it and not have it.”
Experts agree that the younger students are, the more carefully drills should be conducted, with an emphasis on overall safety and listening to adults in unusual circumstances, instead of the specific threat of gun violence.
But almost every American child will eventually confront the existence of school shootings.
In Chicago, Sara Rezvi, a former public-school teacher who now directs an after-school program, recalled a ninth-grade girl asking her during a lockdown drill, “Ms. Rezvi, would you take a bullet for us if somebody walked in with a gun?”
While she is not necessarily opposed to the drills, Ms. Rezvi said schools provided little space for teachers and students to debrief from the fear they cause.