Schools that want to tackle violence need to stop focusing on the prevention of gun and knife crime and instead address acts of “micro-aggression” by teachers and students.

Too many schools concentrate on preventing and responding to extreme acts of violence, often by deploying metal detectors and crisis plans, according to a research paper by US academics. But senior staff must also take action against “subtle undercurrents of violence”, the researchers say in the paper, published in the Journal of Curriculum and Pedagogy.

“These are the aggressive words, gestures and actions that are used to tell people they’re different, that they don’t belong, that they are outcasts,” Jeffrey Brooks, professor of educational leadership at the University of Idaho and co-author of the study, told TES.

“We have to develop a more inclusive attitude in schools or we risk alienating pupils, treating them as outcasts, and that’s what ultimately leads to many different forms of violence, including the sort of shootings that we have seen too often in American schools.”

Professor Brooks said that high-profile cases of mass killings at schools had limited public debate, in the US at least, to gun control and mental health issues. “Too many schools focus only on security to prevent that kind of tragedy happening,” he said. “Once the security and the plan are in place they think they have dealt with the problem.

“But they haven’t. That’s only part of the solution - and the easy part. Teachers and school administrators need to spend more time and effort doing the much more difficult daily job of making a connection with every pupil so they all feel valued, that they belong, that they are part of that school community and have a role to play in it.”

One of the obstacles to achieving this was the size of many schools, Professor Brooks said. “We have allowed schools to become so big and they have become unwieldy. But there is still a lot that can be done.”

UK schools have suffered from similar issues through knife crime, particularly in inner-city areas. The Anti-Bullying Alliance said it agreed with the research, adding that security measures could often have a detrimental effect. Luke Roberts, the charity’s national coordinator, said an overemphasis on security could send the wrong message.

“By putting up knife arches it can say to students that this school is unsafe, that students here carry knives,” Mr Roberts said. “And if there is a culture of unsafety, then students are more likely to feel they need to defend themselves.

“It is far more important to try and deal with the relationships between students, to create role models at the school and to properly train teachers to be able to spot and manage these micro-aggressive incidents.”

The research paper - titled What Can School Leaders Do About Violence in Schools? - recommends that teachers treat students as individuals, not as “numbers”, and avoid labelling them as members of a group. That would help staff to identify the perpetrators and the victims of threats and violence, the study says.

The paper claims that schools could end a culture of violence by changing expectations, holding people to account, building conflict resolution skills and developing programmes to address violent behaviour and build self-esteem.

The authors were inspired to complete the study after the massacre of 20 children and six teachers at Sandy Hook Elementary School in Connecticut, US, in December 2012, by former student Adam Lanza.

Schools must also reflect on whether they are perpetrators or recipients of micro-aggression. “This will help them to understand how subtle violence affects lives and begin to build schools that are non-violent, for all students,” the paper continues.

“It’s not enough for schools just to say that they have a wonderful, inclusive culture,” said Professor Brooks. “They have to show it and work at it every day.”