Tecla, a young Zimbabwean girl, was sold for a few cows by her father to help alleviate the family’s poverty. She was raped by her husband, became pregnant and contracted HIV. Her baby died soon after birth. Tecla was only 12 years old.

At an age when she should have been in school learning and dreaming, Tecla became a child bride. She wanted to be like the other children: playing games, listening to stories, and eventually achieving her goal of being a school teacher. But instead, her dreams were shattered by a marriage she didn’t choose and by sexual violence.

Every day, 39,000 girls like Tecla are forced into child marriage somewhere in the world. That’s 27 girls a minute. And every year, 16 million girls between the ages of 15 and 19 – 90% of whom are married – give birth to children, despite the fact that many are children themselves.

Child marriage is one of the most violent crimes against girls. It can rob them of their childhood, deny them of the chance to complete school and expose them to domestic and sexual violence. Child marriage can also jeopardize girls’ health, increasing both their risk of acquiring HIV and other sexually-transmitted diseases and their chances of dying in pregnancy and childbirth due to early pregnancies and poor access to family planning.

We know that putting an end to child marriage would have tremendous benefits – not only for the girls themselves, but also for their communities. When girls aren’t forced to marry, they can stay in school, will have healthier children and can meaningfully contribute to their families and economies. In fact, each additional year of education for a woman reduces infant mortality by up to 10 per cent. And by enrolling just 10 per cent more girls in school, a country can increase its Gross Domestic Product (GDP) by approximately three per cent. It is a virtuous circle and, as we say at Women Deliver, everybody wins.

It is undeniably difficult to change the cultural and social traditions and norms that make child marriage a common practice in parts of the world. But, it is not impossible. Around the world, passionate advocates, including several of the Women Deliver Young Leaders, are stepping up to demand change in their communities.

For example, in Zimbabwe, the Rising Birds Project is bringing young people together to increase community awareness about the harmful impact child marriage has on girls’ education and health. The project puts pressure on elders and decision-makers to outlaw customary child marriage practices, strengthen the enforcement of new laws and encourage male involvement to bring about change.

Around the world in Bangladesh, Women Deliver Young Leader S.M. Shaikat is also trying to put an end to child marriage. S.M.’s project, known as Jagoroni (Bengali for ‘rising’), has enlisted over 650 young people to help advocate to stop child marriage and dowry-related violence. Youth-led ‘watchdog’ groups use mobile phones and online networks to report dowry violence to authorities and hold local law enforcement agencies accountable.

Young people are also working to ensure that girls – both married and unmarried – are empowered with the youth-friendly sexual and reproductive health information and services they need to protect their health and choose when and with whom to have a baby. Among other things, this includes sexuality education, as well as information about modern contraceptives and where to access them. For example, Maureen Odour is using mobile technologies to provide young people with information about sexual health in Tanzania, and Nargis Shirazi has created digital platforms to spark dialogues about typically taboo topics in Uganda.

Projects like these and others are helping to change the realities of millions of girls around the world. Young people – including young men – are taking matters into their own hands and telling their families, community leaders and policymakers that they will no longer stand for child marriage.

As the world marks International Day of the Girl Child (October 11), let’s join these young leaders in their calls and amplify their voices to put an end to this unacceptable form of violence. Together, we can build a world where 12 year-old girls like Tecla are preparing for school, not for marriage – and on their 18th birthdays, are planning for university or for job interviews, not for another pregnancy.

We cannot stop advocating until every girl, no matter where she is born, has the right to go to school, to choose who and when she marries, and to pursue her dreams. Let girls be girls, not brides.

Katja Iversen is the Chief Executive Office of global advocacy organization Women Deliver. Yemurai Nyoni is the founder of the Rising Birds Project to combat child marriage in Zimbabwe and a Women Deliver Young Leader.