The "peow, peow, peow" of the toy gun has long been silent in the classroom. But new research reveals that by stopping children from playing gun games and pretending to be superheroes, teachers and nursery workers could actually be doing them more harm than good.

Penny Holland, the researcher behind the thesis, used to be a believer in "zero tolerance" to violent play. As a mother, an aunt and a nursery worker, she prevented the children in her care from playfighting, making Lego guns and acting out the Incredible Hulk.

But when she started her research for London Metropolitan University, on which she based the book she is publishing today, she became more and more concerned with the effect the constant telling-off was having on the children - particularly the boys - she worked with.

"We noticed an impact on the half a dozen boys who were persistently interested in weapons and superhero play. We started to notice the effects of our constant negative attention. They became more withdrawn - and set on a behaviour train. They became dispirited."

The boys who were constantly told they were doing a bad thing lost their sense of belonging, or never found it in the first place. Other children saw them as the bad kids and, said Ms Holland.

"We blindly maintain zero tolerance, which rests on such high moral ground, and we become quite blinkered to the children's needs and the impact of that on the children."

Ms Holland led the mainly observational research. She and her nursery co-workers slowly began to work with the children in their games.

"We started working with the play rather than against it which had really positive effects. They became far more socially integrated, they interacted better with the adults, they started to access other areas of the curriculum - their construction skills developed and imaginative play improved and got longer because we weren't interrupting them."

Not only that but other children got involved with the games and the more they developed, the less the games were solely about the weapons. Girls got involved and as the games got longer they moved away from the Batman and Power Ranger themes into their own imaginary scenarios.

The key issue, she says, is about listening to children and not blaming them for going against the status quo of the last 30 years, which Ms Holland attributes to post-war anti-militarism and the rising influence of feminism.

"Children do not determine the influences that they are subjected to. They are subjected to violent images on main stream media. We need to be supporting children in working through the themes of violence. Playing ostrich is not taking on our responsibility as adults towards children," she said.

The drawback is that facilitating such play is time consuming and requires a high level of skill to make sure it goes the right way.

Anne Longfield, the director of the Kids' Club Network, is worried by this too. "It's not that we profoundly disagree. I think pragmatically children need to learn about the world around them and how to behave and respond appropriately.

"Our point was that it's very complex thing we have to deal with and it requires that you have good staffing levels and confident staff. But if you don't have those it can get into difficulty. It requires a very sophisticated approach - otherwise it runs the risk of falling flat."

Pragmatism is one thing, but teachers are more worried about where to draw the line.

John Bangs, the head of education at the National Union of Teachers, said: "We do have some reservations. There's a problem about kids becoming obsessive about guns. Anything that encourages that would worry teachers.

"If it's part of a normal phase - whatever you think of it - then you can be more pragmatic about it. But generally where there's obsession you have to be very careful. I would say that parents have to be very careful about what influences are on the kids."

· Penny Holland's book, We Don't Play With Guns Here, is published by Open University Press