A woman looks down at a memorial for the 19 children and two adults killed on May 24th during a mass shooting at Robb Elementary School on May 30, 2022, in Uvalde, Texas.
CNN  — 

Educators across the country are scrutinizing security plans to see what more they can do to protect students after the killing of 21 people — including 19 children – in one of the deadliest school shootings in American history. It’s an exercise that experts say may do little to prevent another school mass shooting.

The Uvalde, Texas, school district had a safety plan that included its own police force, social media monitoring, and a threat-reporting system to “provide a safe and secure environment” for students.

What worked and didn’t is part of the investigation into the May 24 shooting at a local elementary school where a teenage gunman gained access to the school and came out of a classroom closet firing an AR15-style rifle.

So-called safe corners of schools, secured spaces with two of more sets of doors, and bullet-resistant material built into the entryways are among precautions schools nationwide either had in place or are starting.

In the days following the shooting, schools in Texas reported threats or weapons on campus, and districts across the country are reviewing, updating and reinforcing their threat response policies.

Here’s how schools are protecting students and faculty

In Mississippi’s Jackson County School District, a smaller district with a student population similar to Uvalde’s, Superintendent John Strycker and about 30 administrators met to review safety protocols.

He told CNN he’s losing sleep over finding honest solutions.

The superintendent of 30 years said he can’t guarantee 100 percent safety in schools, despite all the precautionary measures the campuses are taking.

“If someone is focused on doing evil, it can happen, and so we will do the best that we can to ensure the safety of our young people,” Strycker said. “I’m not gonna lie to people because I think you need to work from a playing field of authenticity.”

In a direct response to the shooting in Uvalde, the Los Angeles Unified School District, the nation’s second largest, updated safety protocols to reduce points of entry and explore the use of GPS in mobile apps for first responders. That should address “safe corner designations in schools so that students, employees, families and first responders will know where the most protected area is in case of an incident,” the district said in an online release.

New York City Public Schools, the nation’s largest district, told CNN it is working with partners including the fire and police departments to “make certain that our schools remain as safe as possible in all situations and continue to serve as safe havens for our children.”

New York City schools follow safety measures that include locking all external doors, a required number of safety drills, mandatory town halls dedicated to school safety, and having NYPD school safety agents in every school building.

One of Texas’ largest school districts, Houston ISD, requires all visitors be cleared individually through a doorbell camera by someone inside the building, a policy in place long before the shooting in Uvalde, Dennis Spellman, spokesperson for Houston ISD told CNN. Dallas ISD also has a similar system, which is mirrored by Maryland’s largest school district, Montgomery County Public Schools, as well.

Austin ISD is installing bullet-resistant material at the entryways of all schools and expects to finish this summer, the district said in an online release. In addition, the district is updating cameras on all campuses and installing a new electronic intrusion system.

Technology and training offer limited protection

All that technology and training doesn’t mean anything without trust and communications between police, parents and schools, Amy Klinger, co-founder of Educator’s School Safety Network, told CNN. The nonprofit focuses on school safety and crisis management.

She says there should be discussion about security, access control and law enforcement. But she also wants schools’ daily operations to be assessed.

“We have something written down, and then we have what we really do,” she said. “That discrepancy becomes very dangerous because we are not necessarily following the protocols, or there could be the possibility that we’re creating even more vulnerabilities by the way our facility is run by what we do every day or don’t do every day.”

Arming educators has long been a point of contention across the country, picking up steam once again as an idea to make schools safer.

Matthew Mayer, an associate professor at Rutgers Graduate School of Education who has studied school violence, told CNN it’s not a good policy and “there is no one size fits all answer.”

“Having a gun in the class doesn’t do much to protect kids and, in several ways, actually elevates the risk factors for more injuries,” he said. “So it’s a misguided effort that on the surface may be appealing, but it’s just fraught with pitfalls.”

After the 2018 shootings at Marjorie Stoneman Douglas High School in Florida, Mayer and a group of researchers published an eight-point call to action on preventing gun violence in the country.

“There’s a question here, of this tendency to just have a knee-jerk reaction, but also the tendency for school leaders and politicians to make the appearance and show that they’re doing something,” Mayer said. “It is complex, but I think the argument is we need to take balanced and comprehensive approaches.”

CNN’s Virginia Langmaid and Stella Chan contributed to this report.