Sexual harassment is the norm for almost all young people in England’s schools and colleges yet teachers have done little to tackle it, an official assessment conducted in response to an online campaign against such abuse has found.

Education inspectorate Ofsted said on Thursday that schools had to improve sex education and teacher training to counter the “cultural issue” of harassment and violence that children face regularly from fellow pupils.

The government commissioned the report following widespread publicity in March of revelations on Everyone’s Invited, an online forum in which young people shared experiences of abuse anonymously.

The group said Ofsted’s report was a “positive step forward in the eradication of rape culture”, referring to the wider context of sexism and violence that underpinned sexual harassment in schools.

But it questioned whether meaningful change would follow, given that previous reports, including a 2016 inquiry by the House of Lords, had uncovered similar issues but resulted in little change.

“We’ve had reports in the past and nothing has happened,” it said. “What’s different now?”

Amanda Spielman, Ofsted’s chief inspector, said she was “shocked” by the review’s findings. “It’s alarming that many children and young people, particularly girls, feel they have to accept sexual harassment as part of growing up,” she said.

Nine in 10 of the girls surveyed by Ofsted at 32 schools, including some of those named on Everyone’s Invited, said they or their peers were often sent explicit images or subjected to sexist name calling. Commonplace experiences included being repeatedly asked for nude images or harassed with “rape jokes” on the bus to school.

But pupils spoke of teachers not “knowing the reality” of their lives. The report found schools “consistently underestimate” sexual harassment, and fell short in providing adequate education on relationships and sex.

One girl quoted anonymously in the report said: “It shouldn’t be our responsibility to educate boys.”

Ofsted said schools and colleges should provide high-quality training for relationship, sex and health education (RSHE) teachers, and improve engagement between children’s and health services and the police to respond in a better way to problems.

“This is a cultural issue; it’s about attitudes and behaviours becoming normalised, and schools and colleges can’t solve that by themselves,” Spielman said.

“But schools and colleges have a key role to play. They can maintain the right culture in their corridors and they can provide RSHE that reflects reality and equips young people with the information they need.”

Everyone’s Invited on Wednesday released the names of 2,962 schools it said were mentioned in the testimonies it had received, which it said “reinforces the shocking reality that rape culture is everywhere, including all schools”.

Department for Education statistics show there are 3,456 state-funded secondary schools and 2,331 independent schools of all ages in England.

The government on Thursday announced a limited raft of measures to address the problem.

It will encourage schools to dedicate staff training to handling abuse and issue new guidance on relationships and sex education, and will hold a roundtable discussion on age restrictions for downloading content online.

Mary Bousted, the joint general secretary of the National Education Union, said that to secure long-term change it was necessary to “get the balance in the curriculum right”, encourage reporting and discussion, and properly train teachers.

“Proper support for schools to introduce the new RSHE curriculum can’t be done on the cheap,” she said.

Zan Moon, who in March gathered a dossier of abuse in elite private schools and this week met Baroness Elizabeth Berridge, schools minister, to discuss next steps, also said the government had to commit more time and funding to sex education.

“We need to get to the point where sex education is a priority and standalone in our curriculum,” she said.