NEW YORK (NewsNation) — As the investigation into the mass shooting in Uvalde, Texas, continues to unfold, school districts across the country are reassessing their safety procedures — though many already employ active shooter training for students.

In some instances, the drills are unannounced, taking students and teachers by surprise. It’s an attempt to make the drill seem more realistic, like having a real shooter in the school.

In an active shooter situation inside a school, teachers are the first line of defense.

Watch Live Above: The Rush Hour Roundtable will discuss safety in schools and other issues starting at 6pm ET / 5pm CT.

“The basic fundamental drills still work,” said Ken Trump, a school safety and security expert with more than 30 years of experience. “Lockdowns, police-controlled evacuations, sheltering in place, parent/student reunification, all of those drills work.”

Teachers and staff are supposed to lock classroom doors, shut off the lights and move away from windows as part of active shooter drills.

There’s also the options-based approach, which suggests students and staff should run, hide, throw things at the gunman and fight back as a last resort.

“Options-based training where you’re saying run everywhere creates a target-rich environment; throwing things at a gunman is unrealistic,” Trump explained.

How do you think schools should keep kids safe? Share your opinion in the form below to share it with us. Your comment may be shared during the Rush Hour Roundtable Friday around 7:15pm ET.

Most states require schools to conduct safety and security training. But the National Education Association, which represents three million teachers, said, “There is extremely limited research available on drills’ effectiveness.”

NEA also said unannounced active shooter drills in schools could trigger trauma and high anxiety for students.

Others suggest it’s time for more teachers to be armed in the classroom. It’s allowed in Colorado, Idaho, Florida, Kansas, Missouri, Oklahoma, South Dakota, Tennessee, Texas and Wyoming.

When all else fails, teachers have proven they will step up.

“Every educator I know would stand between harm and their students, but why should they have to,” Trump said.

Another aspect is situational awareness training, which would improve teachers’ perception of environmental elements on how to spot suspicious people and odd behavior.

In Nashville, a group of employees is considered heroes after holding down a man who forced his way into their elementary school. They first noticed him watching the kids during recess. Then, he forced his way inside the school after a teacher tried to stop him from entering. Eventually, three female teachers grabbed and held him until the police arrived. He was later charged with assault and trespassing.