By Brendan O’Brien

(Reuters) – Active shooter drills, a routine in American schools for the last two decades, tend to traumatize students and have not been proven to save lives, according to a report released on Tuesday.

The report by gun safety group Everytown and several parent, student and teacher organizations recommended that schools move away from conducting unannounced drills and drills that mimic gun violence.

“It’s now clear that unannounced active shooter drills are scaring America’s students without making them any safer,” said John Feinblatt, president of Everytown.

Schools across the United States began conducting such drills after the shooting at Columbine High School in the Denver area in 1999 that left a teacher and 12 students dead.

Some 15 years ago, only 40% of schools did drills, but after a rash of school shootings across the nation, that percentage ballooned to 95%. A total of 40 states now require schools to conduct routine drills, according to the report.

The School District of South Orange and Maplewood, in eastern New Jersey, recently made substantial changes to its drills after hearing from concerned parents.

Students and staff are now told about the drill as it is occurring, drills are shorter and teachers now have time to debrief students, according to a letter the district superintendent sent to parents in December.

“Although we hope never to have to use these situations aside from practice and drills, it is important to know that the district will always err on the side of caution to protect our students, staff, and district,” Superintendent of Schools Ronald Taylor wrote.

Active shooter drills vary widely across the country. Some unfold unannounced and involve actors dressed as masked gunmen, teachers being lined up and shot with an airsoft rifle and students as young as 3 years old told to hide in a small space for long periods of time, the report said.

“What these drills can really do is potentially trigger either past trauma or trigger such a significant physiological reaction that it actually ends up scaring the individuals instead of better preparing them,” said Melissa Reeves, former president of the National Association of School Psychologists, in the report.

Evidence is “scant” that drills are effective at preventing deaths in school shootings while there is “extremely limited” research on their effectiveness, the authors wrote in the report.

The report also recommended that drills be tailored to the age of the students and created by a team of administrators, teachers and mental health professionals along with law enforcement personnel. It also said schools should track the effects of drills on students.

(Reporting by Brendan O’Brien in Chicago; Editing by Richard Chang)