Hundreds of school pupils have been either permanently or temporarily excluded in the last four years after being involved in sexual acts, including watching pornography and sharing indecent images, according to new figures.
Data released by 15 local authorities in England shows there were 18 incidents involving boys for every one incident involving a girl.
The vast majority of exclusions were on a fixed-term basis, with 14-year-olds the most likely to be involved in sexual misconduct.
There were 754 reported incidents between July 2013 and April 2017, according to the authorities who released figures under the Freedom of Information Act.
But, the true figure is likely to be much higher as the vast majority of councils contacted said they did not hold the information or refused to disclose it.
The data has prompted calls for sex education to be 'dragged into the 21st century'.
An NSPCC spokesman said: "Every child has the right to feel safe at school.
"Preventing harmful sexual behaviour through proper, up-to-date sex and relationships education is immeasurably better than excluding children after the harm has been done.
"By giving children the right information about sexuality, consent, risks and protection, we teach them how to make healthy relationship decisions, how to treat others and how to know when something is not right.
"Social media, sexting, online porn and dating apps did not exist when sex education was introduced on the curriculum a generation ago.
"It must be dragged into the 21st century, it must be consistent, and it must be offered in every school as part of a broader PSHE (personal, social, health and economic education) curriculum."
In March, the Government announced children would be taught about healthy relationships from the age of four, with sex education compulsory in all secondary schools, from September 2019.
Wednesday's figures show seven cases of children in the first year of school were involved in sexual misconduct during the four-year period, although an age range breakdown was not available from every authority.
There were at least 40 incidents of children below 10 years old - the age of criminal responsibility - disciplined for their actions.
There was a surge in incidents as children reached secondary school - with 66 cases involving 12-year-olds, peaking at 120 for those aged 14.
The figures show the numbers trail off for those aged 15 and above.