Schools in Romeoville, other suburbs using bullet-resistant film on windows amid mass shootings like 1 in Minneapolis, Minnesota

There have been no specific threats at Romeoville High School Wednesday. Nevertheless, the district had extra security on-hand, and extra sensitivity following a mass shooting in Minneapolis.

Some schools in Romeoville and other suburbs are also implementing a new product that could protect students and staff against possible gunfire.

It's called Clear Armor. It is a film that can resist gunfire, keeping it from penetrating windows from the outside. But, from the other side, it can allow investigators to fire at a shooter.

"The evildoers out there in the world are constantly changing the game, and so we have to keep up," Valley View District Security Director Carter Larry said.

With 21 schools and nearly 16,000 students, the Valley View District in the southwest suburbs is one of the largest districts in the state. And it takes safety and security seriously, regularly updating the training for the security officers the district has in every building. And like most other districts, it also runs through age-appropriate drills with students and staff.

"What we may train our middle and high school students in, we don't necessarily train our elementary school students," Larry said.

The alleged shooter in Minneapolis reportedly barricaded the doors f rom the outside so no one could escape before firing shots through the windows. School security experts say the training is continually evolving as the approaches used by criminals keep changing. But the one constant they say is that someone usually has information in advance that could help authorities prevent the shooting.

"We need to make sure, if someone's doing something like this, someone sees something and says something, so we can protect our kids. This is happening too much," school security expert Randy Braverman said.

The clear armor over the windows can be costly. But the school safety director said the added layer of security is worth it. He is working on trying to get grants to pay for outfitting more of the district's schools with Clear Armor.