More than 8,000 children under the age of 18 years old had been accused of sexual offences against other children in the United Kingdom in the last two years alone, the National Society for the Prevention of Cruelty to Children said.
The magnitude and massive number of offences and offenders tends to lead to "question the environment in which they are growing up," NSPCC said.
The charity found that most victims knew their alleged attacker. Most of the perpetrators were teenage boys offending against female friends. The charity likewise found there was a small proportion of female offenders.
Crimes varied from serious sexual assaults, rape, and obscene publication offences.
NSPCC found that up to two thirds of contact sexual abuse on children is committed by other young people.
"It's deeply concerning that thousands of children are committing sexual offences, including serious assaults and rape," Des Mannion, NSPCC Wales' head of service, said.
Peter Wanless, chief executive of the children's charity, blamed the rising numbers to the proliferation of porn and the adults' seeming irresponsible handling of it.
"Easy access to hardcore, degrading and often violent videos on the internet is warping young people's views of what is normal or acceptable behaviour," he said.
"We know that for many older children pornography is now part of life (but) for very young children, such as those of primary school age or younger, we have to question the environment in which they are growing up that has led to them behaving in this way."
Wanless surmised the younger kids are conducting the sexual activity because they saw it and are copying what they've seen.
He also stressed there is still hope for both the offender and the aggrieved party. "These children are not beyond help."
He said therapy could help prevent them becoming adult sex offenders.
Most importantly, their victims need support to overcome what has happened to them. Sexual offences, whether committed by another child or an adult, can have lifelong consequences."