The deadly school shooting this month in Parkland, Florida, has ignited national outrage and calls for action on gun reform. But while certain policies may help decrease gun violence in general, it’s unlikely that any of them will prevent mass school shootings, according to James Alan Fox, the Lipman Family Professor of Criminology, Law, and Public Policy at Northeastern.

Since 1996, there have been 16 multiple victim shootings in schools, or incidents involving 4 or more victims and at least 2 deaths by firearms, excluding the assailant.

Of these, 8 are mass shootings, or incidents involving 4 or more deaths, excluding the assailant.

Mass Murders, 2006 through 2016

Four or more people killed within 24 hours, excluding the assailant

Four times the number of children were killed in schools in the early 1990s than today, Fox said.

Students Killed Per Million in Fatal School Shootings, 1992/93 through 2014/15

Data Source: James Alan Fox and Emma E. Fridel, “The Three R’s of School Shootings: Risk, Readiness, and Response,” in H. Shapiro, ed., The Wiley Handbook on Violence in Education: Forms, Factors, and Preventions, New York: Wiley/Blackwell Publishers, June 2018.

Fox said, however, some policy changes aimed at decreasing school shootings and gun violence in general certainly have merit. Banning bump stocks and raising the age of purchase for assault rifles from 18 to 21 are good ideas, and may lead to a decrease in overall gun violence, he said. But he doesn’t believe these measures will prevent school shootings. “The thing to remember is that these are extremely rare events, and no matter what you can come up with to prevent it, the shooter will have a workaround,” Fox said, adding that over the past 35 years, there have been only five cases in which someone ages 18 to 20 used an assault rifle in a mass shooting.

Fridel said increasing mental health resources for students is another strategy that might improve school safety, calling this a critical need that has been historically overlooked. She also said that the U.S. is facing a desperate shortage of guidance counselors. In 2014-15, the student-to-school counselor ratio was 482-to-1, according to the American School Counselor Association, nearly twice the organization’s recommended ratio.

“You might have students in a very large school who are troubled but who are basically flying under the radar, because you have one guidance counselor for 400 students,” Fridel said.

After the Columbine High School shooting in 1999, schools across the country began holding active shooter drills in which they huddled together in a corner or hid under their desks. Such exercises—which may include someone walking around pretending to shoot students—can be very traumatic, Fridel said, and there is no evidence that they help protect students. “These measures just serve to alarm students and make them think it’s something that’s common,” she said.

Other safety precautions, such as installing metal detectors and requiring ID cards for entry, have also proven ineffective in past school shootings.

Fridel pointed to a few examples.

In addition to being ineffective, Fox said increased security measures of these kinds can do more harm than good. He called the suggestion to arm teachers “absurd” and “over the top.”“I’m not a big fan of making schools look like fortresses, because they send a message to kids that the bad guy is coming for you—if we’re surrounding you with security, you must have a bull’s-eye on your back,” Fox said. “That can actually instill fear, not relieve it.”