The Channel 4 probe into harmful sexual behaviour among schoolchildren found there were nearly 7,000 cases of rape and sexual assault in schools reported to police over the last three years.

Canvassing 50 primary school teachers, half said they felt unprepared in handling the issue and 57 per cent reported having received no training, often leading to incidents being misunderstood.

As part of her special report Cathy Newman spoke to a 12-year-old girl who was sexually assaulted by a male classmate when she was 10.

The youngster recalled how the teacher she reported it to said they didn’t know ‘why you’re making a big deal out of this’, adding: ‘He was just playing.’

With those under 10 unable to be held criminally responsible, the investigation found it was often the victims who are punished.

The girl told Ms Newman ‘nothing bad’ had happened to her abuser when she went back to the classroom: ‘But I was taking the punishment for him.’

The NSPCC defines harmful sexual behaviour as developmentally inappropriate sexual behaviour which is displayed by children and young people.

It can be displayed towards younger children, peers, older children or adults, and is harmful to the children and young people who display it, as well as the people it is directed towards.

There is no universally agreed definition of what harmful sexual behaviour is.

Anne Longfield, the Children’s Commissioner for England, called for additional funding to ‘bring specialists in’ to ‘train teachers and work with children in the classroom’.

One charity which does just that is Tender, and chief executive Susie McDonald told Channel 4: ‘We are hearing from teachers who are creaking under the pressure of what they are trying to do.

‘They are under that huge pressure to do that mainstream work and then they have this on top and they haven’t got that training.’

Ms McDonald added that it is ‘vital’ they receive ‘specialist training so that they are not feeling uncomfortable about the kind of messages they are delivering’.

She said if the issue can be addressed among children as young as possible, it would ‘deal with potential perpetrators as well as potential victims’.

Ms Longfield told said: ‘We need to realise that in this digital world more and more children are getting exposed to inappropriate content from an early age.

‘And that is something that will skew children’s understanding of consent, coercion and what healthy relationships are.

‘We need to make sure we prevent children getting access to that content in the first place.’

Pat Branigan, NSPCC Lead on harmful sexual behaviour, added: ‘It is therefore vital that Government provides proper training so schools can deliver effective and relevant lessons about healthy relationships and sex when the new relationship and sex education syllabus is brought in, in eight months’ time.

‘Children cannot be left to believe that what they see on the internet mirrors real life.’

The charity called on the government to make clear that school cultures play a key role in prevention of abuse and provide educational establishments with practical steps, ideas and guidance to increase their confidence and competence to respond to harmful sexual behaviour appropriately.

It also needs to issue clearer guidance on how schools can best work with children’s social care and mental health services to get all children involved in the abuse the help they need, they added.

There similarly needs to be standardised high-quality training to ensure all schools can confidently provide relationship and sex education (RSE) lessons that are of a gold standard, delivered by a confident and engaged expert.