A growing number of children are being sexually abused by other children, say charities.
They say their helplines have seen a big increase in calls from young people who are being abused.
Freedom of information figures obtained by the NSPCC say more than 5,000 children were reported to police in England and Wales as abusers over the last three years.
Almost all of those accused of the abuse of other children were boys.
Some of those reported were as young as five. More than half of the offences were classified as serious and included rape.
The NSPCC and the Lucy Faithfull Foundation say it is a growing problem.
They think that it is partly because of access to online porn becoming easier, with more children owning devices such as smartphones and tablets.
Jenni says her nine-year-old daughter was sexually abused by a boy of the same age.
She does not want to use her surname because she does not want her child to be identified.
“He aggressively rubbed himself up against her, getting very excited, and telling her what he wanted to do to her in a very graphic way.
“He had his hands around her neck.”
Jenni is convinced the boy was influenced by images he saw online.
“He told her to go home and look at porn sites and then copy what she saw on him,” she said.
“I looked at some of the sites and I couldn’t bear it. I walked away in disgust, it was just too much.
“The images were absolutely horrific.”
Charities believe indecent online material is making young people think that is how they should behave.
The four main internet providers have told the government they plan to put safety filters in homes with children by the end of the year.
Experts say they do not really work because many young people know how to get round them.
A recent government report on young sexual offenders said parents, teachers and social workers often missed warning signs in children who might sexually abuse.
Campaigners say there needs to be more investment in training staff so that they’re able to detect problems early on.
The charities believe blocking porn sites is a start but it is not necessarily the solution.
They think teachers and parents should talk about the damaging effects porn could have on children in an open way.
“He took my daughter’s innocence away,” said Jenni. “It’s just shocking what he did at such a young age.”