In the wake of the shooting in Florida and now another in Maryland, President Trump has triggered a healthy debate about so-called “gun-free zones” in schools – schools which more and more appear to be anything but gun-free.

Trump argued after Parkland a gun-free zone “is like target practice” for school shooters such as the alleged Florida killer, Nikolas Cruz.

“They see that and that’s what they want,” he opined. “Gun-free zones are very dangerous. The bad guys love gun-free zones.”

The next day, Trump pointed out to a room full of Governors at the White House, “You have a gun-free zone, it’s like an invitation for these very sick people to go there.”

Critics pounced.

“He is just utterly missing the point of the law,” said a former staffer for then-Sen. Herb Kohl, D-Wis., who led the charge on gun-free-school zones in 1990.

Leaving mass shootings entirely to one side, she said, communities confronted “the very serious danger posed by a variety of criminal actors around schools and involving guns.”

Let’s rewind.

On May 16, 1986, a shooting in Wyoming’s Cokeville Elementary School left two dead and a towering 74 injured.

Then, on January 17, 1989, another shooting at Cleveland Elementary School in Stockton, Calif. left six dead and 32 injured.

Around this time, the U.S. Centers for Disease Control and Prevention (CDC) found that 135,000 guns were brought to school each day.

An alarming one in five urban high school students reported having a gun fired at them at school, and a 1993 survey found 40% of students in central cities said they knew someone personally who had been killed or injured by gunfire.

Democrats’ response? Why, gun control, of course.

Sen. Kohl introduced the Gun-Free School Zones Act (GFSZA) in February, 1990. The measure was rolled into the Crime Control Act of 1990 and signed into law by President George H.W. Bush – granted, a Republican president – on November 29, 1990.

What happened?

First, between 1992 (note: not 1990 or 1991) and 2015, the percentage of students who reported carrying a weapon on school property during the previous 30 days decreased from 12% to 4%.

Second, GFSZA advocates argue students at least felt safer at school: “From 1995 (note: not 1990, 1991, 1992, 1993, or 1994) to 2015, the percentage of students who reported being ‘afraid of attack or harm’ at school dropped substantially, from 12% to 3%.”

Third, the law’s cheerleaders argue, CDC statistics show school-associated violent deaths dropped from 57 in the 1992-93 school year (note: neither 1990-1991 nor 1991-92) to 33 in 2009-10. However, the figure actually peaked in 2006-2007 at 63, and is up substantially since 2009-2010.

Fourth, another rah-rah data point: a 2017 report found the number of crimes against students has plummeted more than 80% since 1992 (note: not 1990 or 1991). Problem solved!

Unfortunately, while it’s true the crime victimization rate at school declined 82%, the rate away from school declined 88%.

Worse, the serious violent victimization rate at school declined only 50%, while the rate away from school plunged 91%.

So after the GFSZA, schools actually got safer more slowly than the rest of the community, which during the period was exiting the crack wave.

Regardless, none of these statistics compares the period before Bush signed the GFSZA to after it.

So I crunched the numbers on school shootings per year, number killed per year, and number wounded per year before the GFSZA (1968-1990) and after it was put in place (1991-2018).

Get ready.

In the period after enactment of the Gun-Free School Zones Act, school shootings more than doubled from 2.7 per year to 6.9 per year, an increase of 155% from the period before enactment.

Those wounded in school shootings nearly doubled from 8.8 to 13.9 per year, an increase of 58%.

And killings in school shootings nearly tripled, from 2.7 per year to 7.9 per year, an increase of 192%.

Figure 1: Number of school shootings per year, number killed in schools per year, and number wounded in schools per year before the GFSZA (1968-1990) and after it was put in place (1991-2018). Data source: http://triblive.com/news/education/safety/13313060-74/heres-a-list-of-every-school-shooting-over-the-past-50-years.

A closer look at the data bears out that the number of school shootings has increased over time, and generally accelerated after the GFSZA was signed into law in 1990. That said, there is an exception that may prove the rule: The Supreme Court declared the GFSZA law unconstitutional in United States v. Lopez, 514 U.S. 549 (1995). Only later did then-Attorney General Janet Reno for Bill Clinton propose changes that conformed it to the Constitution. Those changes were signed into law in 1996, but doubts remained at least until 2000 about the measure’s ability to withstand a court challenge. During that period, school shootings declined, then rose again afterwards.

Figure 2: Number of School Shootings By Year, 1968-2018. Data source: http://triblive.com/news/education/safety/13313060-74/heres-a-list-of-every-school-shooting-over-the-past-50-years.

*Note: 2018 figure only through February 14, 2018.

An obvious question this raises is whether homicide rates increased more generally at the same pace and with the same timing. Does the spike in school shootings just track a spike in killings?

The answer? No. The homicide rate actually dropped steeply in this period. The crack wave was ending, sending murder rates back to levels not seen since the early 1960s.

Figure 3: U.S. Homicide Rates, 1885-2010. Source: http://www.thetruthaboutguns.com/2013/12/foghorn/guns-violence-united-states-numbers/

More specifically, the firearm-related deaths for youths ages 15-19 in particular followed an almost identical pattern, spiking from 1970 to the early 1990s, then plunging back to prior levels – nearly the opposite of the school shooting pattern.

Figure 4: Firearm-Related Death Rate Among Youth Ages 15-19, 1970-2014. Source: https://www.childtrends.org/wp-content/uploads/2014/10/70_tablescharts.xlsx.

Thus the increase in number and lethality of school shootings can be explained neither by homicide rates in general nor firearm-related death rates among youth.

Another counter-argument would be that mass shootings have increased more generally over that period, which is true. Is the increase in school shootings before and after the US declared them off limits to law-abiding gun owners merely an artifact of an increase in mass shootings more generally?

The answer again is no.

Now, according to data compiled by the far-left Mother Jones, it’s true the percentage of those wounded in mass shootings who were shot in schools was cut in half after the Gun-Free School Zones Act passed, from 32% of mass shooting injuries between 1982 and 1990 to 14% from 1991 to today.

Also, this drop took place despite the percentage of mass shootings that took place in schools growing from 11% to 17% of all mass shootings at the same time.

But the apparently positive change appears to be because schools shootings became so much more lethal. The percentage of mass shooting fatalities that took place in schools tripled, from 7% before the Gun-Free School Zones Act to 21% afterwards.

So: Half as many injuries in schools among mass shootings, but only because three times as many died in a greater number of mass shootings there.

Figure 5: Percentage of mass shooting injuries, attacks, and fatalities that took place in schools before the GFSZA (1968-1990) and after it was put in place (1991-2018). Data source: https://www.motherjones.com/politics/2012/12/mass-shootings-mother-jones-full-data/.

This is a problem.

It is true that the largest spikes in school shootings followed far on the heels of the GFSZA’s enactment.

To explain that, Second Amendment opponents might point to the expiration of the assault weapons ban in 2004.

In response, Second Amendment supporters might point instead to the bonkers Obama Administration’s Promotion of Random Offenses and Misdemeanors by Insane Students Escaping justice (PROMISE) program which paid schools to persuade law enforcement agencies to let youth get away with criminal activity, especially if they were “of color,” which may (or may not) explain why the Broward County Sheriff’s office deliberately ignored what they admit was 23 and may have been 45 warnings of Cruz’ criminal insanity.

Regardless, the numbers bear out the horrific impression to which Trump is giving voice: After America declared schools gun free zones, school shootings increased and became more deadly.

By these measures at least, Trump is right, and his critics are wrong.