A fifth of women say they were exposed to unwanted sexual contact as schoolgirls, a survey suggests.
In a poll 22% reported having some experience of sexual touching, groping, flashing, sexual assault or rape while they were "in or around" school, children's charity Plan UK said.
Ten per cent of those said the contact happened sometimes or frequently, with the rest saying it 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."