Gordon Brown has pledged £8.5bn to get every child in the world into school by 2015. But haven't we seen all this before? Hilary Wilce reports

Gordon Brown wants all of the world's children to be in primary school education by 2015. He believes education is the key to ending poverty, and has announced that the UK will spend £8.5bn over 10 years (more than four times than in the previous decade).

"In 2005, Make Poverty History forced governments to make promises on aid," Brown said in Mozambique, announcing this commitment. "Now it is time for us to keep our promises. None is more important than the Millennium Development Goal that by 2015 every one of the world's children is able to go to school."

Never before have such sums been put behind global education, and campaigners are delighted. But will they be put to good use? Does creating more school places help poor children and promote economic growth? Or will the cash seep away into a quagmire of poverty and corruption?

Research does confirm a link between education and development. But it's a complex one. "Basic education is critical for development," says Leon Tikley, a senior education lecturer at Bristol University and the head of an international research project on education quality. "But you can expand your basic education system and be in a situation where you've got 80 children in a class, no roof on the classroom, and children writing on slates leaning on other children's backs. And a lot of teaching can be didactic and teacher-centred. So you have to ask what outcomes you can expect under such circumstances, and the answer is very poor ones."

Also, he points out, in the "Asian tiger" economies, it was the expansion of secondary and tertiary education, not primary schooling, that fuelled lift-off. "If you have that, then you are not dependent on other countries for expertise. The mantra that you need to build up basic education first, because that gives you the biggest return in your investment, is being challenged. Many people are moving towards a more varied approach."

Expanding primary schools is not easy. More places mean more teachers, books, stationery, furniture and officials. Low-income countries also have to address the many issues that keep children out of school.

Long journeys, early marriage, the cost of uniforms and books, and the need for children to work at home make it hard for poor parents to send their children to school, even when the places are there. And then there are the fees. When Kenya abolished primary school fees in 2003, enrolments shot up to 84 per cent, and there is now an international campaign to abolish basic fees.

Even water is critical, as the charity WaterAid points out. Children who spend hours collecting water or taking animals long distances to drink have no time for education, while water-borne diseases make many children too ill to go to school. In Madagascar alone, three and a half million school days are lost a year because of poor sanitation. And a lack of lavatories can make it hard to recruit teachers to schools, and keep girls at home when they have their periods.

Then there is the question of local needs. People in countries emerging from conflict have different educational priorities to those tackling an HIV/Aids epidemic or those in places where basic schooling is already widespread.

"The more basic education you have, the more your returns on basic education are reduced," says Christopher Colclough, a professor of the economics of education at Cambridge University. He points out that when only a small number of children go to school, school leavers are much more likely to find paid employment than when larger numbers have some schooling. "And while there are huge benefits from basic literacy, there are a large number of primary school systems where children leave without gaining this. So, what goes on inside schools, in terms of the teachers, in terms of having fewer than 50 in a class, and of the books and writing materials that are available, is crucial."

However, more schooling also brings returns in terms of family health and reductions in neo-natal mortality, he points out. "So one of the best investments you can make is in having girls go to school."

According to figures quoted by the Chancellor, every extra year a girl goes to school reduces the mortality rate of her children by 8 per cent. Educated women are also three times more able to protect themselves against HIV/Aids.

Even the Campaign for Female Education supports a quarter of a million girls through secondary schools in Africa, and helps them develop economically active lives afterwards. It trains and supports women teachers, and works to create safe school environments. "We're in a great moment right now, with a lot of leadership in the area of education," says Khadijah Fancy, the director of research. "But basic education on its own is not enough to sustain change. When it comes to fertility rates, economic growth and the health of future generations, you don't see that sort of knock-on effect for basic education. You see it at secondary level."

Developing education must be a long-term issue, she says. "You have to ask if what you're doing is going to affect children in 20 years' time."

Long-term development is key, agrees David Archer, the head of international education for Actionaid International, which welcomes Gordon Brown's commitment to long-term, stable financial support. Most education spending goes on costs, including teachers' salaries, he points out, and governments need to know they can afford to train and employ teachers over a span of years.

"Teachers are the most important thing. Between 15 and 30 million more will be needed between now and 2015 if we are to meet the Millennium Goal. However, many countries are placing people in school with just a few weeks' basic training. It's big in French-speaking West Africa, and 500,000 have started work in India in the last three years. This deprofessionalisation is very worrying."

He also points to a deep contradiction between the demand of the IMF that poor countries rein in their public spending, and the investment that is needed to build an education system. "The IMF looks at things over a short three- to five-year time-frame, but you can never make a rational case for education if you are only looking at things from this perspective." The IMF also wants countries to keep inflation down, yet rapid economic growth in South America and Asia happened when inflation there was running at 10 to 15 per cent. "There is more flexibility about public spending these days. But when it comes to inflation, Gordon Brown is unlikely to confront that. He's attached to low inflation."

The effectiveness of the programme will come down to the ability of governments to spend the money wisely, and the international community providing the right support. It is hard to oppose Gordon Brown's initiative, but it remains to be seen whether there is anything new about it, beyond the size of the sums involved.

'Many parents do not value education and want their children at home to work'

Tanzania is working hard to build its education system. Poverty and history had left it with some of the world's lowest school participation rates. But a stable government and a commitment to investmentmeans it is now one of the World Bank's "fast track" countries, attracting increased global aid. Five years ago, debt relief helped abolish primary school fees. Enrolments leapt by 50 per cent and the government is now starting to develop secondary schools. Last year, secondary enrolments went up from 6 to 10 per cent.

Primary school pupils and new secondary schools are now a common sight. Nearly 500 secondaries have been built in the past six months. More teachers are being trained, and students are happy with the methods.

But the problems are huge. Bilula Simfukwe, who runs a secondary school in Urambo, western Tanzania, has bare labs, few books and a shortage of teachers. "Also, many parents still do not value education and want their children at home to work."

"Sometimes you have to walk four hours to reach a school. At the end of the day, your feet can be aching so much!" says Elisonguo Mshiu, a district education officer.

College and university places are like gold dust, and jobs, especially in rural areas, are scarce. Students who finish secondary school can be disillusioned by the lack of opportunities available.

But a growing economy and predictable aid has enabled the country to increase spending fourfold in four years and to set long-term goals. "I see a bright future," says Stella Bendera, an education adviser in the President's Office of Public Service Management. "Awareness of education is growing."

Dedicated individuals are working hard to make that happen. Headteacher Mary Mwageni, who runs Wasa secondary school outside Iringa, in southern Tanzania, is short of teachers, books and classrooms. "When I came here from the town, it seemed so remote. There was not even a house for me. I thought, 'Oh dear. They want me to be a missionary.' And then I thought, 'Well, if they want me to be a missionary, that is what I will be! If I work hard, maybe I can improve the situation.'"