Some schools with chronic violence and weapon violations have installed metal detectors at their entrances, screening students for contraband as they arrive. That conversation has started in Worcester, where police have arrested several students in the past few weeks for possession of firearms, among other potentially deadly weapons.

A security audit is underway and metal detectors are on the table, although there is community and City Council resistance.

Ken Trump, president of Cleveland-based National School Safety and Security Services, believes metal detectors are an unsustainable, knee-jerk political reaction. He cautions against their use for practical reasons like cost, and because they are often seen as a replacement for better strategies.

Trump has been a school safety consultant for 30 years and Congress has invited him to testify on the topic four times since 1999. He also provided testimony to the task force that was formed after the Sandy Hook shooting and frequently appears as an expert on national news programs.

School officials in Boston and Springfield told MassLive metal detectors are beneficial. Still, Trump urges decision-makers to carefully consider the costs and consequences.

"There's a great deal of pressure put on schools ... to create some visible, tangible signs of security, and oftentimes that equates to some form of equipment," said Trump. "One gun is one too many (but) the devil is in the details of implementation."

In order to do the job, a metal detector would have to be coupled with other measures that simply are not realistic. First and foremost, they must be in use around the clock, 365 days a year, to prevent someone from stashing a weapon, Trump said. All ground-floor windows need to remain permanently shut so no one can pass anything into the building. No one can prop open a door, even temporarily, and every entrance and exit would need to be manned.

Some of these measures could violate local ordinances and fire codes. And everyone, young and old, student and staff, parent and visitor, would need to be screened every time they enter, no matter the purpose.

If you want to go see a play, report for athletic practice or games, use the gym outside school hours, or attend a public meeting, you'd have to go through the metal detector. Even just dropping off your child's lunch or going to a parent-teacher conference would require the same.

The cost is not necessarily worth it

What if it breaks? Can the school district or the city afford to fix it?

The one-time installation cost can buy a sense of security "instead of investing in more longer-term strategies that are focused on people," Trump said.

Springfield public schools utilize metal detectors and have found them helpful. District spokesperson Azell Cavaan declined to tell MassLive how many schools have them, citing security concerns.

The equipment was purchased from Security Detection, based in Holliston. Springfield's Open Checkbook website shows the city paid $16,475 for five metal detectors and sent the company another $2,799.50 for an unspecified "invoice" in fiscal 2015, along with $1,000 for a "repair." A separate line item titled "Metal detector and handheld wand" shows a cost of $4,044.95.

Even if the money is in the budget, one could argue that it's an unnecessary expense for most communities.

Metal detectors create a false sense of security

In 2013, a 14-year-old in Atlanta was shot in the neck inside a school that used them. Administrators admitted the machines were "not operable" that day.

A Minnesota school with a metal detector, guards and fencing was the site of a mass shooting in 2005 that left seven people dead. The gunman killed an unarmed security guard manning the detector, and the other guard fled for his life.

She hesitated to say that the school staff member would be "trained," but "they do go through some kind of proper familiarization process." Each school's security team coordinates with the district's central office to ensure the work is done properly, and administrators are expected to report problems with the metal detectors that may lead to vulnerabilities.

Trump said metal detectors can be useful in large urban districts like Los Angeles and New York City. Keep in mind, though, that the size and location of a school has nothing to do with the students' ability to get their hands on weapons, he said. Gangs and drug dealers are not the only ones with guns; everyday law-abiding citizens have them, as well, and it's not impossible for a child of any age to throw one in his backpack or stash it in his locker.

There are better ways to find out about a gun in a school

Trump said the best way to find out about a weapon in school is to build relationships with students and make them feel comfortable reporting it to a trusted adult.

Cavaan, the Springfield spokesperson, said metal detectors are just one element in a broad strategy.

"They are one of several tools we use to help ensure student and staff safety. We don't rely solely on metal detectors, but they are an important part of our security, particularly at the high school level," she said. "The metal detectors have done their job in terms of alerting staff to items that maybe shouldn't be brought into the school."

Every school in Springfield has a buzzer system for visitors, and all are expected to sign in at the front office, said Cavaan. Staff, when possible, will escort the visitor to his or her destination. The Quebec Unit, the city's version of school resource officers, also circulates between schools to keep an eye on things, and cameras monitor every common area.

"It's a multi-pronged approach to student and staff safety," she said, adding that the district is always looking at security developments and trends around the region. "It's the only thing that's more important than teaching."

Last year, the National Center for Education Statistics released data from the 2011-2012 school year, showing 2.7 percent of public schools required students to pass through a metal detector every day. Spot checks were slightly more prevalent at 5 percent.

Anyone planning school security measures should remember that students are not the only potential threats, he said. A parent, a staff member or someone with no connection to the school could stroll in with a gun, and a reaction plan must be in place.

A student is more likely to be bullied than shot

At every school, no matter the size or place, staff should have two-way radios to quickly initiate a lockdown and stay in contact during an emergency, according to Trump. They should be visible in lunchrooms, regularly check restrooms, test their crisis response plans, monitor social media for threats, and remember that guns are not the only danger in school.

Building a sense of trust and credibility with the community is crucial, Trump said. When a school hires a resource officer, parents need to know about it and be aware of the officer's role. They should be notified of changes, additions and subtractions made to any plan. That way, if there is a crisis, parents will feel more confident their children are safe and know where to direct any concerns.

The bottom line

While Trump argues against installing metal detectors at all, Cavaan believes they're useful as part of a much bigger plan. The district can afford to buy and maintain them, and they have paid off by, at least periodically, keeping dangerous contraband out. Many of Trump's suggestions are in place at Springfield public schools.

Trump's advice boils down to this: "Invest in your people, not products." His organization has conducted focus groups and surveyed interested parties for years to develop its suggested methods, and a common takeaway is that students can find a way to bypass a metal detector.

"Most people will tell you, 'If somebody really wanted to get a weapon in here, they could,'" he said. And if a gun or a knife slips through, the school needs a whole system of contingencies and trained personnel in place, ready to respond at a moment's notice.