A photo of Caroline Previdi, one of the victims from the 2012 Newtown, Ct. elementary school shooting (AFP PHOTO/Emmanuel Dunand)

When the 550 students at a private school in Virginia Beach recently returned to class, they walked into classrooms newly monitored by gunshot-detection technology. Acoustic sensors tucked high on walls listened for the distinct sound of gunfire, able to pinpoint its location and alert authorities. The technology also greeted students heading back to schools in Newark, Calif., and Reynoldsburg, Ohio.

These schools are among the few early adopters of military battlefield tools that today are being deployed to address a nightmare scenario much closer to home: the school shooting. The technology doesn’t stop gunfire, but supporters say it can limit the carnage by speeding up the emergency response.

Interest in these systems appears to be growing, seeded by the three major companies that make the devices and driven by school administrators grappling with how to keep students safe. Inquiries also spike after each school shooting, the latest coming Monday when a history professor was fatally shot by another professor at Delta State University in Mississippi.

But the technology has created discomfort, too. Its emergence is seen by some as a tacit admission that school shootings have become an unavoidable part of the American landscape, that classrooms are targets that need to be hardened. Some school safety experts doubt the value of gunshot-detection technology. But the industry compares its devices to fire alarms — common-sense measures that can save lives.

The demand for this military-inspired technology in schools and the apprehension it causes can be traced to the fear that reverberates from the massacre nearly three years ago at Sandy Hook Elementary in Newtown, Conn., where a gunman killed 20 first-graders and six adults.

In fact, one school near Newtown is installing a gunshot-detection system right now.

“Unfortunately, there’s a market for this,” said Christian Connors, chief executive of Shooter Detection Systems, which is working with the Connecticut school. He declined to name the school because of contractual reasons.

At Newark Memorial High in California, Principal Phil Morales said he sees the gunshot-detection sensors — about the size of smoke detectors and placed in every classroom and hallway — as just another safety device. His school of 2,000 students does not have a violence problem. No metal detectors meet students at the doors. But Morales, a former police officer, said he welcomed the ability to detect gunshots.

“I think all schools should have this, just like fire alarms,” Morales said.

Just as fire alarms don’t prevent fires, gunshot-detection technology doesn’t prevent shootings.

But, Morales said, if gunfire is detected, he gets an “active shooter alert” sent to his desktop computer and his cellphone with precise details about where the shooting occurred in the building. Police and first responders get a similar message. The instant notification allows him to more effectively direct lockdown procedures, ushering people away from a shooter, and aid the emergency response, Morales said.

Critics view the gunshot-detection systems, which can cost $10,000 to $100,000 depending on the size of a school, as failing to address what they say should be the real goal — preventing gun violence.

“It’s a mistake to install, and it shouldn’t even be on the board for consideration,” said school safety consultant Ken Trump, who favors staff training and mental health efforts.

Ron Stephens, executive director of the nonprofit National School Safety Center, said one manufacturer asked his center to endorse its gunshot-detection tool. He declined, in part because his center doesn’t promote products. But he also considers the technology to be misguided.

He noted that hasn’t tampered enthusiasm for the devices.

“I’m a little surprised at the number of schools getting these installed,” Stephens said.

The system at Newark Memorial High was installed this summer as a test project by ShotSpotter, a company best known for providing police with outdoor gunshot detection services in crime-addled areas of Washington, St. Louis, New York and other cities.

ShotSpotter chief executive Ralph Clark said his company wasn’t looking to expand into the schools market until the Newtown shooting. That’s when the inquiries began, asking whether the ShotSpotter devices could be modified to protect students.

Its first effort came last September, when ShotSpotter’s SecureCampus system went live at the Savannah College of Art and Design in Georgia.

On Aug. 27, at nearby Savannah State College, a student was fatally shot during a fight in the student union. For some, this highlighted the need for the technology.

School shootings are a worry everywhere, Clark said. “This is sadly becoming the new normal.”

Another supplier, Shooter Detection Systems, said that in the last year it has placed devices at one school in Methuen, Mass.; four more in California; and another in Virginia Beach. It said it is in talks to install the technology at 36 schools on the West Coast. The company also has done work in factories, a hospital and two airports.

Shooter Detection Systems said its clients did not want to be identified. The Washington Post was able to locate the Virginia Beach school and talked with an administrator there, who spoke on the condition that the school not be named. The administrator, while thankful for the technology, didn’t want to draw undue attention to the campus.

“It’s kind of sad that schools are needing to do this,” the administrator said, “but it’s a reality.”

The administrator also said the school, like most schools with this technology so far, did not pay full price for the system.

The system at the Virginia Beach school is based on Boomerang, which was created by the Pentagon and Raytheon BBN Technologies to help U.S. military forces locate sniper fire on battlefields in Iraq and Afghanistan.

The school version listens for gunfire and looks for muzzle flashes using infrared sensors, a system that might be particularly useful in a situation such as the one at Virginia Tech in 2007, when a gunman killed 32 people as he roved among multiple buildings on a vast campus.

To buttress their case for installing the devices, the gunshot-detection companies point to a 2013 FBI study of active shooter cases.

The study examined 160 incidents in the United States from 2000 to 2013. It found that these shootings were rare but were increasing, almost tripling in the study’s second half to 16.4 a year. A total of 486 people were killed over the 14-year span. The study captured high-profile shootings such as the ones at Virginia Tech, at Fort Hood, Tex., in 2009 and at a movie theater in Aurora, Colo., in 2012.

Twenty-seven of the 160 shootings occurred in schools serving kindergarten to 12th grade.

Twelve other shootings took place at colleges and trade schools.

The study also noted how quickly the shootings unfolded: 70 percent lasted less than five minutes.

In Reynoldsburg, Ohio, gunshot-detection devices now monitor one of the high schools. It was installed by Battelle, located in nearby Columbus. The science and technology firm, a major U.S. defense contractor, had approached the school about doing a pilot project.

“Why not take this opportunity to try out this system?” said Todd Hutchins, district communications director, explaining why the district took up Battelle on its offer.

Hutchins said he didn’t find it depressing to have the capability to detect gunshots inside a school.

“If it helps unease, then that’s great,” he said. “I have a feeling this is going to be the norm.”