Online pornography is turning children into copycat sexual predators, doctors and child abuse experts warned yesterday as they demanded tighter supervision of school toilets, playgrounds and internet use.

A four-year-old boy has ­required a chaperone to stop him assaulting other children in “sex games” at a South Australian ­kindergarten, The Australian can ­reveal.

And doctors are treating more girls in their mid-teens for pregnancy, sexually transmitted ­infections and physical injuries resulting from “aggressive sex” inspired by online porn.

Emeritus professor Freda Briggs, who has advised federal and state governments, police and church groups on child safety for 30 years, has accused schools and childcare centres of ignoring or covering up a spate of “child-on-child abuse”.

She has blown the whistle on a regional kindergarten in South Australia where a four-year-old boy allegedly sexually assaulted young children late last year.

“The staff allegedly ignored anal and oral sex accompanied by threats and secrecy, dismissing it as ‘normal developmentally ­appropriate behaviour’,” Professor Briggs says in her newly published submission to a Senate inquiry into the impact on children of online pornography.

“Parents removed victims from the kindergarten for their safety … the boy who initiated the behaviour is now accompanied by a supervising adult, at considerable expense to the taxpayer.

“Nevertheless, his behaviour has allegedly continued in the out-of-school-hours childcare centre and other children have re-enacted it.

“It is alleged that no one asked him where he had learned to play these ‘sex games’.”

The South Australian case follows the recent removal of a six-year-old boy from Sydney’s prestigious Trinity Grammar School after a group of Year 1 boys was found performing sex acts in the school toilets and playground.

South Australia’s Department for Education and Child Development declined to identify the kindergarten but said it was “working with the families involved”.

“The department treats inappropriate sexualised behaviours with the utmost seriousness and any incidents of this kind are investigated and managed directly by senior staff,” a spokesman said yesterday. “The welfare of the children remains our priority. The department will continue to offer support to them and the broader community in an ongoing basis.

“This includes ongoing work with Freda Briggs, who has separately endorsed the state’s mandated child-protection curriculum which is taught in every year level between reception and Year 10.”

Australian Medical Association vice-president Stephen Parnis yesterday said the internet was exposing children to sexually ­explicit content that taught that sex was about “use and abuse”.

He warned that doctors were treating more girls in their mid- teens for unwanted pregnancy, sexually transmitted infections and physical injuries.

“There are increasing levels of aggression and the physical harm resulting from sexual acts is becoming more apparent,” he said.

“Many of them have felt pressure because unless they are compliant with their partners’ requests and demands, they are somehow not seen as being a good girlfriend.”

He said more young women were demanding cosmetic surgery on their genitals because “they’re comparing themselves to images they see on the internet …”

National Children’s Commissioner Megan Mitchell yesterday said children’s access to online porn was “influencing their attitudes and risk-taking behaviours”.

“They’re much more likely to think the kind of sexual activity that goes on in pornography is what they should expect in an intimate partner relationship and they take risks, including anal sex,” she said.

Professor Briggs says the South Australian case is “typical of what is happening elsewhere”.

Her submission, tabled in the Senate, lists a litany of attacks on children by classmates, including a six-year-old boy who forced oral sex on kindergarten boys in the school cubbyhouse and a group of boys who followed a five-year-old girl into the toilets, held her down and urinated in a “golden shower”.

Professor Briggs reveals that during interviews with more than 700 children for an Australian Research Council study, some boys aged six to eight told her “fun” activities with their fathers included watching pornography online because “that’s what guys do”.

She says victims, perpetrators and their families all required counseling and therapy. “The problem is that neither teachers, police, nor social workers appear to be trained to take these behaviours seriously and respond ­appropriately,” her submission says. “There is no attempt to investigate how, where or from whom the instigator acquired his inappropriate sexual knowledge and therefore there is no attempt to stop the problem at source.

“Failure to handle child-on-child abuse satisfactorily usually means that the problem increases as victims become copycats.”

She warns that children are ­accessing pornography on computers and phones and sharing their findings in the playground.

“Some of the images show violent sex and girls being sexually ­assaulted anally, vaginally and orally by multiple males,” she says.

Professor Briggs calls for better supervision of school toilets, change rooms and camps, saying some schools “try to shove the problem under the carpet”.

“When staff are inadequately informed, serious incidents such as rape have been dismissed as ‘boys will be boys’, or it’s ‘normal sexual experimentation’, when it clearly isn’t,” she says.

“In the private sector of education, with risks to enrollments in mind, some parents have specifically been asked not to report child sexual abuse to police to protect ‘the good name of the school’.

“When school managers have fulfilled their mandatory notification obligations, some have minimised what happened, referring to rape as ‘inappropriate behaviour’, thus avoiding an investigation.”