You don't have to tell Grace Mwangi, aged 12, about the importance of education. She is one of 50 students in the fourth grade of a primary school in Kibera, a sprawling slum in Nairobi. The overcrowded classroom lacks books and pencils. The teacher is untrained. And the cost of running the school falls on parents who live in grinding poverty. Yet education is seen as a source of hope and an escape route to a better life. "People without education have no future except hardship," says Grace, adding: "If I work hard and pass my school tests, I can be a doctor."

Visit any slum or poor rural village in Africa and it is hard to avoid being struck by the drive for education. Amid squalor and deprivation, parents and children demonstrate an extraordinary level of commitment in pursuing opportunities for learning. Political leaders must share in equal measure their resolve and ambition.

Just over 10 years ago, governments around the world made an important promise to the world's children – that they would have universal basic education by 2015. We are now just four years away from that deadline. And we are one primary school generation from a broken promise. The headline facts speak for themselves. There are 67 million primary school-age children out of school. Millions more start school only to drop out before they have learned to read, write and count; and many of those in school receive an education of such poor quality that it does little to prepare them for the job market.

To make matters worse, there are signs that progress towards the 2015 target is slowing. The United Nations Educational, Scientific and Cultural Organisation (Unesco) has warned that, on current trends, there could be more children out of school in 2015 than there are today. That would be an indictment of the international community's effort to deliver on the promise of education for all.

The word "crisis" is sometimes over-used in international development. But the slow progress towards universal basic education represents a crisis of the first order. It consigns millions of children to lives of poverty and diminished opportunity. It hampers efforts to tackle youth unemployment in the poorest nations. And it weakens the international effort to reduce child mortality. Empowering Africa's girls through education could prevent 1.8 million deaths of children under 5 each year, according to the UN.

The damage does not end there. In a new report, we at the Global Campaign for Education set out evidence that accelerated progress in education could increase per capita economic growth in the poorest countries by as much as 2 per cent a year. That would give a powerful impetus to efforts to reduce poverty and create jobs. Achieving that result would, of course, require increased investment, but for every $1 in new spending, the education growth premium would generate $10 to $15 in increased wealth.

So, what has to happen if we are to keep the promise of providing all of the world's children with the chance of a decent quality education? National governments have to take the lead. Countries such as Tanzania, Ethiopia and Mozambique have demonstrated that rapid progress is possible. The key ingredients for success include increasing investment in education, removing school fees, developing effective teacher training systems, and an unrelenting commitment to equity. International co-operation also has a vital role to play. Many of the poorest countries cannot afford to increase investment in education on the required scale. To translate the commitment to universal primary education into real opportunities, sub-Saharan Africa alone needs another one million teachers. Bluntly stated, the international aid system for education is failing the world's children. Too many donors have broken their promise to ensure that countries with credible education plans receive the support they need. The poorest countries need around $16bn annually in aid to achieve the 2015 target. They currently receive just $2bn to $3bn.

But it is not just the aid system that is failing. Education has drifted to the periphery of the agendas of the G8 and the G20. There is nothing in education to compare with the innovative financing that has characterised the fight against HIV/Aids, malaria and tuberculosis. And there is nothing to compare with the passion, energy and commitment of the public campaigning that galvanised G8 leaders to drop Africa's debt.

This has to change. It is time to renew the promise of education for all – and time for a new deal for kids in the poorest countries. Leaders of the G8 are being asked to support the creation of a new global fund for education that would tap into increased aid, philanthropic donations and innovative financing. An immediate priority is support for countries emerging from forgotten conflicts, such as South Sudan.

Our report recognises the importance of looking beyond aid. That is why it sets out the case for a public-private partnership that links Africa's schools and teacher-training institutions to the universe of learning opportunities opened up by information and communication technologies. The region is currently excluded from that universe by the high cost of connecting to the Internet. Broadband connection costs in Mozambique, for example, are four times higher than in the UK. And we are looking beyond governments, donors and the business community to the power of public opinion. We need a global campaign to "train a million teachers" – a campaign that mobilises finance and galvanises political leaders to act. It is through education – which Nelson Mandela has described as "the most powerful weapon you can use to change the world" – that we build hope, realise ambition, combat poverty, strengthen democracy and sow the seeds of innovation and economic growth.

When they meet, G8 leaders have a chance to put education where it belongs – at the centre of the global poverty reduction agenda. We realise that there are competing priorities and that resources are constrained. Making a difference will take bold leadership, iron resolve and commitment. But if a 12-year-old girl in a Kenyan slum can try so hard to get an education, doesn't she deserve our support?

Gordon Brown MP is Co-Convener of the High Level Panel on Education, part of the Global Campaign for Education