A Virginia school district announced that it will add ballistic film to all of its school’s entry points to deter attackers from entering the facilities.

Poquoson City Public Schools says that it has partnered with Mid-Atlantic Technology Services, a safety and security company, over the past four years to install ballistic film on windows and doorways of all four school campuses.

“We believe that we are as safe as we can make it,” Poquoson City Public Schools Superintendent Arty Tillett told local media outlets. “I learned a long time ago that there’s no perfect plan, but you just put one layer on top of the other and on top of that to keep our kids and staff as safe as possible.”

The purpose of the bullet-resistant film is to slow down an attacker from gaining entry with a gun or deterring them entirely. Tillet said that campus doors have already been treated with ballistic film. School leaders hope that the windows will be treated by the middle of the school year.

“We’ve done it in a phased-in approach,” Tillet said. “The first part of this was to get all of our entryways covered, any glass at an entryway. So, that’s been done, and so now we’re looking at any exposed glass on the exterior.”

Tillet added that the school district features not just ballistic film, but security systems, armed school resource officers and cameras.

This summer, the ASTM F12 Security Committee introduced a new ASTM universal standard that will help school districts choose from a range of high-performance products that will add additional protection to schools.

The push for a standard in security products follows a history of mass shootings in schools throughout the country. The most recent was at Robb Elementary in Uvalde, Texas, where 19 children and two teachers were murdered by a lone gunman with a high-powered rifle.