"My pen is my sword."
I saw this slogan inscribed on the wall of the Ayesha-e-Durrani School in Kabul last May.
The school, named after the first woman to open a girls' school in Afghanistan, was severely damaged during the war. Today, it welcomes 1,600 girls from Grade 1 through high school. One of its pupils told me that thanks to education "we now know the difference between knowledge and ignorance."
With these simple words, she said it all. Education opens minds. It gives girls and boys the freedom to choose -- to choose between ignorance and knowledge, to choose lives they wish to live.
This is true in Afghanistan and across the world. But everywhere, this human right is being violated.
This is what Malala Yousafzai has brought to the attention of the world. Her courage reminds us that the right of girls to quality education is the fight for a better world.
For far too many, being born a girl means a life sentence of injustice. Across the world, girls still bear the heaviest burden of poverty, marginalisation and violence.
There has been progress since 2000 when we set the Millennium Development Goals and the Education for All objectives. More children than ever before are going to primary school, and we have halved the number of girls out of school. But we are still falling short, and progress is stalling.
There are today 31 million girls out of primary school, and a similar amount out of secondary school. UNESCO's new figures show that half of all children out of school in the world live in conflict-affected situations. Meanwhile, only a tiny share of humanitarian aid is spent on education.
The price we pay for this is unacceptable. Malala knows this, so do those girls in Kabul, and we must never tire in making their case.
The facts are clear. Every extra year of schooling for a girl delays early marriage and reduces family sizes. Any child born to a mother who can read is 50 percent more likely to survive past age five. Girls who make it past primary schooling are five times more likely than illiterate women to be educated about HIV and AIDS. In a word, girls' education is one of the best investments a country can make. This is a human rights issue; it is also a security issue.
To harness this power, we must act in three directions.
First, we need to raise awareness -- to help girls everywhere in overcoming barriers and to bolster the resolve of Governments in cracking down on gender-based violence.
Raising awareness means raising money. UNESCO estimates that we face a funding gap of $26 billion a year to provide all kids with a basic education.
Benefits far outweigh costs. Every $1 spent on a child's education yields $10-$15 in economic growth over that person's working lifetime. Everyone stands to gain. This is why UNESCO organized with the Government of Pakistan a High-Level Advocacy Event last December in Paris, and created the Malala Fund for Girls' Education, to which Pakistan donated $10 million.
Second, we must target the weakest links of girls' education.
It is not enough to enroll girls -- we need to ensure they stay the course, all the way through secondary school. This calls for schools to become safe spaces. This demands curricula and training to prevent gender-based violence at all levels of education. This requires sharper policies to reach the unreached and to prevent girls from dropping out.
Third, we need to put education at the top of the political agenda.
This is the aim of the UN Secretary-General's Global Education First Initiative that UNESCO is helping to steer forward -- to make the case for quality education as the best investment for inclusive, sustainable development. This must stand at the heart of the post-2015 global development agenda.
We must also build education into all peace-building efforts, because there is no better way to break cycles of violence and set communities on the path to peace. Education and peace-building must be linked with longer-term development, not left under-funded.
Too many girls, in too many countries, are held back simply because they are girls. They face violence, they are forced to work, they are married off young.
Malala Yousafzai and those girls in Kabul are standing up for change. All of us must rise to support them, to change attitudes, to build a world that is more just and equal. We must do all this, because every child has the right to know the difference between knowledge and ignorance, because the pen really is mightier than the sword.
This post is part of a series produced by The Huffington Post in association with the A World at School campaign to mark Malala Day. Malala Day will take place at the United Nations on July 12, 2013 -- the 16th birthday of Malala Yousafzai, the Pakistani girl who was shot by the Taliban for wanting to go to school. On that day, Malala will address 500 young campaigners as part of a special youth takeover of the United Nations. For more information, visit aworldatschool.org.