Many forget what it was like in the playground while older and female teachers often disapprove of "play" fights, although boys can enjoy them.
A new study based on observations of 44 Sheffield boys aged six to eight found that only 1 per cent of "play" fights - usually between friends - degenerated into something more serious. But teachers reckoned around 30 per cent of real fights resulted from playing.
Professor Peter Smith, of Goldsmiths College, London, one of the researchers, believes teachers may be overestimating the problem because they focus on "trouble-makers". These were boys the researchers identified as most likely to be involved in real fights, whether because they were bullies, or disliked by other children.
The researchers, who say girls tend not to "play" fight, found that most boys had done so and enjoyed it. Engagements were governed by rules and conventions, and only tended to turn nasty when someone unintentionally hurt their opponent, or a trouble-maker was involved who deliberately provoked the other.
A total of 41 per cent of teacers said it was quite often hard to distinguish real from play fighting. Professor Smith says they may be basing their judgment of the number of fights that turn nasty on those disputes involving the "trouble-making" children, who are disproportionately involved.
"It's a mistake to come down hard on play-fighting because it's not a bad thing. It's normally a friendly activity children enjoy, so why try and stop it. But it's important to be able to distinguish it from real fighting," he added.
Teachers and lunchtime supervisors should look out for certain signs when trying to distinguish between real and play fighting, such as:
Facial expressions. Are children smiling, or are they serious, red-faced and distressed?
The attitudes of other children. Playfights are not usually of interest to other children because they are normal. A real fight will quickly gather an audience, wanting to see who's going to win.
Are the blows, kicks or punches actually hitting home? It may look ferocious, but the participants may not even be making contact.
This week, Professor Smith also told the British Psychological Society annual conference that trainee teachers need to be taught to deal with bullies.