By Lin Taylor

LONDON, May 2 (Thomson Reuters Foundation) - As teacher Tanya Mathiason flicked through a slideshow to display diagrams of male and female genitalia to primary school children in northwest London, no one flinched or giggled.

Instead, the students eagerly discussed the meaning of the words: female, genital, and mutilation.

"Break those words down: what does female mean? What does genital mean? What does mutilation mean?" said Mathiason, the head of pastoral care at Norbury School in the culturally and ethnically diverse neighbourhood of Harrow.

Take action: Not One More: Help Global Citizen End Female Genital Mutilation

"It means when someone cuts off stuff?" replied one student.

"Harm?" said another.

By the time they leave Norbury School, all 640 students — both boys and girls — would have learnt about female genital mutilation (FGM), a ritual that usually involves the partial or total removal of the external genitalia including the clitoris.

An estimated 137,000 women and girls in England and Wales have undergone FGM, according to the National Society for the Prevention of Cruelty to Children (NSPCC).

Read more: FGM Happens in the UK, But Is Obscured by a Very British Silence

FGM can cause chronic pain, menstrual problems, recurrent urinary tract infections, cysts, and infertility. Some girls haemorrhage to death or die from infections. It can also cause fatal childbirth complications in later life.

As FGM is mostly carried out between infancy and 15, school principal Louise Browning said she wanted the students to start learning about it in the third year, at about seven years old.

"I became more aware that FGM was happening to girls at a much younger age than I thought," Browning told the Thomson Reuters Foundation.

"Who's to say that we don't have survivors in our school? I felt I was letting down my girls by not raising this," she said. "Our end goal is for this practice to stop."

Read more: Britain Just Pledged to End Female Genital Mutilation by 2030

Browning and her team worked with the National FGM Centre, run by children's charity Barnado's and the Local Government Association, to devise age-appropriate lessons, which they began teaching in Norbury School in 2015.

It is one of only a handful of primary schools in the country that teaches students about FGM, but raising awareness among parents and children was necessary, she said.

FGM mostly affects immigrant communities from various countries including Somalia, Sierra Leone, Eritrea, Sudan, Nigeria, and Egypt — a demographic that is well-represented in the Harrow school.

"Many of our families, our children, come from FGM-practising communities so it is really important that they have this knowledge, that they leave here at 11 (years old) knowing what this practice is about," said pastoral manager Mathiason.

Read more: London Lawyer Acquitted of Forcing Daughter to Undergo FGM as Punishment

FGM is performed by Muslims and Christians and by followers of some indigenous religions. People often believe FGM is required by religion, but it is not mentioned in the Koran or the Bible.

"Most people who do it think it's in their religion ... but no religion actually tells you to do that," said 11-year-old Khadija, who has learnt about FGM since she was seven.

"It's just shocking because it's most likely to be parents who would do it. They're the ones who love you and care about you, but instead they want to harm you," she added.

In March, a London solicitor accused of forcing his daughter to be circumcised was acquitted, increasing pressure on police and prosecutors who have yet to secure a conviction for FGM more than 30 years after it was outlawed.

The prosecution was only the second to be brought under FGM legislation introduced in 1985.

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FGM is underpinned by the desire to control female sexuality, but beliefs around the practice vary enormously. Many believe it purifies the girl, brings her status in the community and prevents promiscuity. Uncut girls risk being ostracised.

Sonita Pobi, head of training at the National FGM Centre, said the lessons helped children make sense of the practice and know who to turn to for help, regardless of their cultural background or religion.

"It's about giving children the vocabulary to speak up when something is wrong. It's about making children aware about the hidden form of abuse that may happen to them," said Pobi.

After learning about FGM at Norbury School, 11-year-old Oliver said he felt empowered to help classmates and friends.

"When I first learnt about it, I was quite scared because it was happening. But once I knew quite a bit about it, I knew that I couldn't really sort out the situation, but I would know who to speak to," he said.

His classmate Naylen, also 11, agreed.

"I think the FGM lessons are good for children to learn because ... we could make a change to all of these harmful activities," he said.

(Reporting by Lin Taylor @linnytayls, Editing by Katy Migiro; The Thomson Reuters Foundation is the charitable arm of Thomson Reuters that covers humanitarian issues, conflicts, land and property rights, modern slavery and human trafficking, gender equality, climate change and resilience. Visit http://news.trust.org to see more stories)