Like anywhere in the world, the start of the lesson on sex education is accompanied by rowdy jokes and giggles from its young audience. But in the deprived Brazilian city of Cod, in the northern state of Maranhao, the class comes with a difference - it is led by students.
Across the state, one of the poorest in the country, one in five babies was born to a girl aged 10-19 in 2010. Reports of sexual exploitation and violence are widespread. With the Fifa World Cup starting next week, charities have stepped up their campaigning against "sex tourism" and the government has pledged to take action. But in deprived and remote parts of Brazil, it will take more than a flurry of publicity to make a lasting difference.
In Cod, a project led by children's charity Plan International, backed by pharmaceutical giant AstraZeneca, is getting teenagers to act as mentors and teach their peers about safe sex and avoiding exploitation. Rather than relying on traditional classes, young people are trained to deliver workshops on sexual health, puberty, women's rights and homosexuality.
Eduardo Santos, 18, one of the peer educators, said the system was more effective than regular lessons. "People were embarrassed at first, but the project has rules inside the classroom about respecting others' opinions and that anything said inside doesn't leave the room, creating an environment of trust," he told TES. "I had friends who took part and they said they were grateful to me. They said the knowledge I passed on meant they learned a lot through what we're doing, which is great."
The project, part of Plan International's Youth Health Programme, has been running for three years in partnership with 24 schools in the area. Official data is expected at the end of next year, but those working on the scheme have reported a drop in the number of teenage pregnancies. Based on preliminary results, it has been renewed for another two years.
Teenagers taking part in one of the sessions at a state school in the nearby town of Timbiras said they felt more comfortable discussing issues around sex with people closer in age to them.
As part of the workshop, teenagers of both sexes were asked to consider a range of statements related to sex and gender and to discuss social norms and biology. The session dealt with gay relationships, stereotyping and sexual rights.
One 14-year-old boy said: "These are our friends so it's much easier to express ourselves. There's much more equality than we have in the classroom with teachers."
As well as the classroom workshops, the project also puts on theatre events and lectures outside school. According to Plan, a street drama event dealing with sexually transmitted diseases was attended by 300 people. One of the current campaigns is to promote safe sex and encourage girls as well as boys to carry condoms to address the high incidence of HIV in the country.
"Young people here feel more comfortable and more at ease talking to people of their own age about these things because they don't have the courage to talk to their parents about it," said Leandro Nascimento, one of the project's coordinators.
"For a long time, the reality in Brazil was that teenagers and children were seen as people who didn't exist, who didn't have rights. Here in Cod, sex lives start at 10 and children start sexual activity to earn money."
Antonio Gonalves, director of the Luzenir Matta Roma school in Cod, said that empowering students to help their peers had led to marked changes in young people's attitudes to sex.
"The socio-economic profile of the students here is quite disadvantaged," he said. "This project prioritises students' self-esteem and this has brought improvements. I hope in the future we will have more projects here to overcome these problems, but we need more investment."
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