Teachers must assume sexual harassment, online sexual abuse and sexual violence are occurring in and around their schools and colleges even when there are no specific reports, Ofsted has said.
Education institutions must now have a "whole school" approach in place to address sexual harm, following a recent review that found harassment has become normalised among students.
An Ofsted report published earlier this month found children often do not see the point of reporting sexual harassment because it happens so frequently.
The watchdog visited 32 state and private schools and colleges and spoke to more than 900 young people about sexual harassment after thousands of testimonials were posted on a website.
Ofsted inspectors were told that boys are sharing "nudes" among themselves like a "collection game" on platforms such as WhatsApp and Snapchat, while some girls have experienced "unwanted touching in school corridors".
Future Ofsted inspections will now look at how schools and colleges tackle all forms of sexual abuse and harassment, the regulator said.
It has updated its inspection handbooks to help schools and colleges develop a culture that recognises and addresses sexual harm, and issues sanctions where necessary.
The changes will come into force from September when routine inspections resume.
Inspectors will look at how schools and colleges handle individual allegations of abuse between children and young people, and the preventative measures in place.
Preventative measures include behaviour policies, pastoral support and how well the relationship, sex and health education curriculum is taught.
Sean Harford, the national education director at Ofsted, said: "The findings from our recent review have revealed just how commonplace sexual harassment has become in schools and colleges.
"So, even when there are no specific reports, schools and colleges must assume that it is taking place and plan to address it accordingly."
He added: "We will expect schools and colleges to have created a culture where sexual abuse and harassment is not acceptable and never tolerated.
"And where pupils are supported to report any concerns about harmful sexual behaviour and can feel confident they will be taken seriously."
Under the new guidelines, teachers must be aware of the factors that can increase a child’s vulnerability to sexual abuse, and also the barriers that might prevent students from reporting incidents.
These factors include mental illness, domestic abuse, children with additional needs and those groups which are at greater risk of exploitation and/or feel unable to report abuse – such as girls and LGBT children.
Ofsted warned institutions that do not have adequate processes in place will likely be marked as ineffective at safeguarding – impacting their overall grade.
It added that its inspectors will not investigate individual allegations of abuse, but will ensure they are reported to the appropriate authority if necessary.