Almost 30,000 reports of sexual assaults by under-18s against other children have been made to police in the last four years, including 2,625 alleged attacks that took place on school premises.
The data, released by 38 of the 43 police forces across England and Wales in response to freedom of information requests, shows that reports of peer-on-peer abuse rose from 4,603 in 2013 to 7,866 last year: an increase of 71 per cent.
But almost three-quarters of cases (74 per cent) reported to 36 forces between 1 April 2013 and 31 May 2017 resulted in no further action, according to the figures obtained by BBC's Panorama programme.
The investigation found that 2,625 reported sexual offences – including 225 alleged rapes – that were carried out by under-18s on other children took place on school premises, including primary-school playgrounds. These attacks occurred across 31 force areas.
'It's the people failing you'
Figures from 30 forces show reports of sexual offences by children aged 10 and under have more than doubled, from 204 in 2013-14 to 456 in 2016-17.
This Friday’s Tes includes an online-safety special, with new figures explaining the extent of child sex exploitation and sexual exploitation online.
The magazine includes an exclusive first-hand account of the work of the London Metropolitan Police units that investigate sexual crimes against children, as well as an exclusive interview with a Lorin LaFave, who is a campaigner for internet safety, and whose son Breck was murdered by a man who groomed him online.
During the Panorama programme, some children – anonymised to protect their identities – spoke about how they’d felt bullied, let down and isolated after reporting abuse.
"It's not what actually happens that has the worst effect on you – it's what comes after it,” one said. “It's the being disbelieved – it's the people failing you.”
Another said: "We'd be on the bus. They'd throw things at me or shout things and make comments. It's not always even him – it's his friends."
Abused children and their parents also spoke of struggling to get help from schools or the authorities – a problem highlighted by Tes in March.
One victim said during the Panorama programme: "There was no talk about the police, or telling his parents, or taking it further, it was only really, 'Oh block him,' or 'Stay away from him in lesson.'"
Another child's parents said: "I couldn't actually believe that we're in the 21st century in Great Britain and we are allowing sexual abuse to continue...and for victims to go unsupported."
Government guidance tells teachers they have a legal duty to report allegations of sexual assaults on children by adults.
But Panorama claims there is no such duty when a child is accused of sexual assault, with schools advised to follow their own child-protection procedures.
However, the Department for Education told the programme: "Sexual assault is a crime and any allegation should be reported to the police."
An investigation by the Press Association earlier this year revealed that children as young as five had been excluded from school for sexual misconduct.
The data released by local authorities showed that hundreds of school pupils had been permanently or temporarily kicked out of the classroom in the past four years after being involved in sexual acts, which included watching pornography and sharing indecent images.