Matthew Mayer, a professor of educational psychology at Rutgers’ Graduate School of Education, says that among experts the best solutions to school shootings are not really in dispute: basic gun control, more and better mental-health services and a robust national threat-assessment program. We also need to help educators create an atmosphere where students who hear about a potential threat feel comfortable sharing that information with adults. (Many student shooters, including Gabe Parker at Marshall County, hint about their plans to at least one other person or tell them outright. Getting those others to inform teachers is one of our best options for preventing shootings from happening in the first place.) In February, Mayer and his colleagues circulated an eight-point document titled “A Call for Action to Prevent Gun Violence in the United States of America,” which summarized these and other key actions needed to reduce the risk of school shootings. So far, 4,400 educators and public-health experts have signed it. But political will is still missing. “We keep revisiting the same conversations every five or six years without learning or changing much of anything,” Mayer says. “Armed guards and metal detectors make it look like you’re doing something. You get far fewer points for talking about school climate and mental health.”

From the inside, a mass shooting can feel distinctly unchartable. But Reed — and Pynoos, and Melissa Brymer, his colleague at the National Center for Child Traumatic Stress — say that while each school shooting is different in its particulars, several features are common to all. For example, Brymer says, it can be the secondary trauma that undoes a school’s recovery. “After a shooting, everyone wants to talk about how to find the next shooter so that this doesn’t happen again,” Brymer says. “But that’s not what the school itself needs to focus on. We’ve had suicides, car accidents, overdoses.” For a school that’s already traumatized, she says, these follow-up events can be incredibly devastating. Brymer advises schools to conduct mental-health screenings before anniversaries, to find the people who are struggling most and help them. The hierarchy of hurt can split in surprising ways. For the most part, people closest to the carnage are the most traumatized, and people farther away are less so. But any teacher might be plagued by any number of things, including what they saw and how they responded in the moment. One educator might flee the building in a panic, leaving his students behind, only to be devastated by guilt afterward. Another might behave heroically, then seethe with resentment over not getting enough recognition. Each will need counseling and support to fully recover.

Teachers are at the quiet center of this recurring national horror. They are victims and ad hoc emergency workers, often with close ties to both shooter and slain and with decades-long connections to the school itself. But they are also, almost by definition, anonymous public servants accustomed to placing their students’ needs above their own. And as a result, our picture of their suffering is incomplete. We know that the trauma that teachers experience after a school shooting can be both severe and enduring. “Their PTSD can be as serious as what you see in soldiers,” says Robert Pynoos, co-director of the federally funded National Center for Child Traumatic Stress, which helps schools coordinate their responses to traumatic events. “But unlike soldiers, none of them signed up for this, and none of them have been trained to cope with it.” We know that teachers who were least able to protect their students in the moment tend to be especially traumatized. “For teachers, the duty to educate students is primary,” Pynoos says. “But the urge to protect those students is deeper than that. It’s primal.” And we know that their symptoms can include major sleep disturbance, hair-trigger startle responses and trouble regulating emotions.

For all the fear they inspire, school shootings of any kind are technically still quite rare. Less than 1 percent of all fatal shootings that involve children age 5 to 18 occur in school, and a significant majority of those do not involve indiscriminate rampages or mass casualties. It has been two decades since Eric Harris and Dylan Klebold ushered in the era of modern, high-profile, high-casualty shootings with their massacre at Columbine High School in Littleton, Colo. According to James Alan Fox, a criminologist at Northeastern University, just 10 of the nation’s 135,000 or so schools have experienced a similar calamity — a school shooting with four or more victims and at least two deaths — since then. But those 10 shootings have had an outsize effect on our collective psyche, and it’s not difficult to understand why: We are left with the specter of children being gunned down en masse, in their own schools. One such event would be enough to terrify and enrage us. This year, we had three.

Teachers were the first responders. Before police officers and medics arrived, they gathered sobbing, vomiting, bleeding kids into the safest rooms they could find, then locked the doors and kept vigil with them through the stunned and terrified wait. They shepherded the injured to hospitals in their own cars. And they knelt on the ground with the ones who were too wounded to move, stanching blood flow with their own hands and providing whatever comfort and assurance they could muster.

There's also potential for confusion within the CRDC itself. While this particular item refers clearly to "a shooting," the previous item asks about a long list of incidents, some involving "a firearm or explosive device" and others involving "a weapon."

A separate investigation by the ACLU of Southern California also was able to confirm fewer than a dozen of the incidents in the government's report, while 59 percent were confirmed errors.

For comparison, the Everytown for Gun Safety database, citing media reports, listed just 29 shootings at K-12 schools between mid-August 2015 and June 2016. There is little overlap between this list and the government's, with only seven schools appearing on both.

Our reporting highlights just how difficult it can be to track school-related shootings and how researchers, educators and policymakers are hindered by a lack of data on gun violence.

In 161 cases, schools or districts attested that no incident took place or couldn't confirm one. In at least four cases, we found, something did happen, but it didn't meet the government's parameters for a shooting. About a quarter of schools didn't respond to our inquiries.

How many times per year does a gun go off in an American school? We should know. But we don't. This spring the U.S. Education Department reported that in the 2015-2016 school year, "nearly 240 schools ... reported at least 1 incident involving a school-related shooting." The number is far higher than most other estimates.

Numerous studies have suggested an association  between exclusionary discipline  practices and an array of serious educational, economic and social problems, including school avoidance and diminished educational engagement; decreased academic achievement; increased behavior problems; increased likelihood of dropping out; substance abuse; and involvement with juvenile justice systems. All of these problems are costly to the victims and to our society. They drive up the public costs associated with the aftermath of violence, substance abuse counseling, unemployment or underemployment, policing and the justice system, and much, much more.

These social-emotional learning practices have been found in hundreds of studies to reduce negative behavior and violence in schools, making schools safer while also increasing academic achievement. The guidance builds on what we know about how to increase school safety through “conflict resolution, restorative practices, counseling and structured systems of positive interventions.” The guidance also provides research-based resources to address students’ mental health needs, as well as proven practices that make students feel more connected to school and part of a community, so they are less likely to engage in negative and harmful behavior.