In the months after 17 people were killed in a massacre at Marjory Stoneman Douglas High School in Parkland, Florida, school districts around the country are preparing for the grim possibility that one of their buildings could be the site of the next mass shooting.

Schools nationwide are training teachers and other staff on how to prepare and defend from an active shooter. Others, like the site of a previous mass shooting in Newton, Conn., are being completely redesigned with students’ safety in mind. And some students are being equipped with equipment meant to protect them, like bulletproof backpack inserts and clear plastic bags designed to prevent students from bringing weapons into the classroom.

These and other measures are being undertaken while parents, teachers, students and lawmakers grapple with other ways to address America’s gun crisis, including through laws that make it tougher for would-be assailants to get weapons in the first place.

Watch TIME’s video above to learn more about what’s being done to protect kids in the classroom.

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