Additional armed security has been drafted into classrooms in Pennsylvania after a school district came under scrutiny for tasking students and staff with using rocks to thwart mass shootings.
The Blue Mountain School District in Orwigsburg kitted out all 200 of its classrooms with buckets of river stones to ensure youngsters and their teachers could "fight back against an intruder rather than wait passively for an intruder to attack".
Superintendent David Helsel said he did not want students to be "helpless victims" in the event of a shooting, adding that river stones would be "more effective than throwing books or book bags or staplers".
But with the unusual defence strategy having attracted widespread scrutiny since its announcement last week, further armed security is being introduced.
Mr Helsel said media attention afforded to the idea had "increased concern regarding the possibility that something may happen".
The additional armed security will be visible from Monday, with all of the five-gallon buckets of river stones to remain in place at each of the five schools for use as a "last resort".
Robert Conroy, director of organising with gun control group CeaseFirePA, had described the addition of river stones to the classrooms as a "tragic" way of attempting to keep students safe.
"We should be talking about real reform of gun laws," he said.
"It is so unbelievably tragic that our society has come to a point where schools have to arm themselves with buckets of rocks to defend them against active shooters."
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The district has also installed security cameras, secured building entrances and fortified classroom doors in an attempt to thwart attacks.
It came as hundreds of thousands of Americans joined rallies in Washington and around the worldon Saturday calling for tighter gun laws in March For Our Lives protests, organised by survivors of the massacre at Marjory Stoneman Douglas High School in Parkland, Florida, last month.