A fifth of British women say they were exposed to unwanted sexual contact while at school, but most of them did not report the incident, according to new research.
A poll by children's charity Plan UK revealed 22% of women over 18 reported having experience of unwanted sexual touching, groping, flashing, sexual assault or rape while they were "in or around" school.
A further 10% said the incidents happened "sometimes" or "frequently", with the remainder saying they took place "rarely".
Three in five (61%) said they never reported incidents to a teacher or another person in authority.
Tanya Barron, of Plan UK, said: "Our findings show that schoolgirls have been suffering in silence for decades.
"We know that these experiences can have a devastating impact on their lives.
"Unwanted sexual contact can affect a young girl's self-esteem and educational achievements.
"It is extremely worrying to see that girls have been experiencing unwanted sexual contact in or around school since at least the 1940s."
The findings are based on over 3,700 interviews with Britons aged 18 and over, including more than 2,000 women.
Across both genders almost one in 3 adults (32%) aged between 18 and 24 and one in ten who are 65 or over (11%) reported experiencing unwanted sexual contact in or around school, according to the research.
Plan UK are calling for a number of measures including support for teachers to prevent and manage incidents of unwanted sexual contact in schools.
Ms Barron added: "This is a global problem. Girls and boys need clear messages that unwanted sexual contact in or around school is not acceptable."
A Government spokesman said: "No young woman should be made to feel unsafe or suffer harassment in any circumstance.
"Sexual assault is a crime and must always be reported to the police. Sex and relationship education is already compulsory in all maintained secondary schools and we expect academies and free schools to teach it as part of the curriculum.
"We are also working with leading headteachers and practitioners to look at how to raise the quality of PSHE teaching, which includes sex and relationship education."
Useful helplines and websites:Suggest a correction
Victim Support - Visitvictimsupport.org.uk or call 0808 168 9111
Sexual Abuse Referral Centres - Find a SARC
Rape Crisis - Visit rapecrisis.org.uk or call 0808 802 9999
The Rape and Abuse Line - Visit rapeandabuseline.co.uk or call 0808 800 0123 (answered by women) or 0808 800 0122 (answered by men).