At least one in five British women experienced unwanted sexual contact while they were in school, a children's charity reported yesterday, and of that number, nearly half said the abuse was frequent.

After surveying more than 2,000 women in Britain, Plan UK found that 22 percent had experienced sexual touching, flashing or rape during their school years. Around 60 percent of women who said they were sexually harassed as a child have never reported the incident.

"School should be a completely safe space. When sexual harassment happens in schools, it dramatically reduces girls' ability to engage in all of their opportunities," Lucy Russell, Plan UK campaign manager, told the Thomson Reuters Foundation. "It can deeply affect somebody's confidence. Obviously it can have serious physical harm, depending on the act. And that means perhaps they'll start dropping out [of school]. It can have long-term knock on effects for their education."

One in three British women between 18 and 24 said they had experienced unwanted sexual contact as a schoolgirl, while one in 10 women over 65 had similar experiences. Russell said that including older women in the survey showed that sexual harassment was not a new phenomenon, rather it is deeply entrenched in society and largely tolerated by women regardless of their age. "This is a behaviour that girls have been told to expect. They're being told... you should just put up with it."

While the survey did not factor in harassment through social media and text messaging, this is a major concern for young girls, she said, as many are being pressured into distributing sexual photos of themselves by peers or boyfriends.

She added that school-based sexual abuse is one of the reasons why globally 66 million girls do not attend school. In some countries, girls are more susceptible to harassment on their way to and from school, or when using school toilets. UNICEF estimates around 150 million girls around the world have been sexually assaulted. "Whether it's Lagos, Lima, London, (girls are) telling us: ‘We can't get into school, we feel unsafe,'" Russell said.