“When we first approach them, I always ask the same thing - why are you not in school?” says Agnes Chiravira, a big, warm woman. Gap-toothed and confident, she strides through the chaotic main market in the dusty northern Ghanaian town of Tamale, with a purpose.

She is here to bring education and hope to thousands of children who live and work on the streets.

In this country, where seven out of 10 people live on less than a dollar a day, lack of rain, poor soil and bad housing are driving many rural Ghanaians to leave for the cities to find work.

An estimated one in four children does not attend primary school and, increasingly, youngsters are dropping out to help support their families.

They work in the teeming markets - either as porters or selling anything from hot food to charcoal. Others simply beg.

Street children are the most visible manifestation of the 42.5 million primary-age youngsters across sub-Saharan Africa who are missing out on school. Living on the street they are the hardest group to reach.

Since 1995, Chiravira has managed to persuade thousands of street runaways, orphans and children from broken homes in the shanty town to attend several hours a day of basic education in preparation for entering the mainstream school system.

The drop-in centre, called “Tizaa”, which means “Our home”, provides basic lessons in numeracy and English as well as lunch for those children for whom this may be their only daily meal.

Classes have started and Isabelle, the young teacher in the first class, is struggling to form the children’s hands around their chalk to make letters.

It is common for working children to find it physically difficult to do their alphabet.

This Youth Alive project sponsors several hundred children to learn a trade or continue into formal education. They work as carpenters, mechanics and seamstresses. Loans are made to families of sponsored children - many have gone on to set up shops and workshops in their chosen trade. They then take other street children and train them. This year a boy has won a scholarship to college, funded mostly by the UK-based charity ActionAid.

“I saw very much my own childhood in most of the children: quarrelsome, eye-for-an-eye types,” says Chiravira.

Children like Atta, aged eight. His father, once relatively comfortable, fell victim to a stroke and his brothers cheated him out of his land. Today they have to beg together in the market. “My mother left us and my family makes fun of us,” he sighs. All of a sudden, the rage and the pain well up into fierce tears. “People don’t even look at us when we beg.”

Agnes pulls him to her, wipes his eyes. “You will be strong and you must study and you will live.”

“Give me a child for a year and you will see the growth,” she says, “The children we have educated will make sure that their children don’t go back on the streets - we are breaking this cycle of poverty.”

Ghana is one of six Commonwealth countries that the World Bank says have drawn up comprehensive plans - agreed with donor countries under a “fast-track” financing initiative - to tackle poverty and bring in universal primary schooling.

The government can’t afford to fund universal education on its own, but donors have yet to back their promises to plug any financial gaps with their own money via the fast-track initiative. Until they do, the best hope for children like Atta, who have fallen through the educational net, lies with the work of grassroots programmes such as Youth Alive.

Back on the streets with Hussein, a project worker and a former street child himself, we find Latifa, aged nine. “One of four children,” says Chiravira.

Latifa’s father is a watchman. He is an alcoholic who suffers from tuberculosis. Her mother abandoned her and her brother.

Barefoot and filthy, she sleeps with him at the main bus stop. The only regular food she gets is from the “Tizaa” and from a porridge seller who is kind enough to give her a bowl of food before she goes to beg.

“I want to be a nurse,” she says in a tiny sing-song voice.

An impossible dream? “No,” says Chiravira. “When I first found her she just wanted to beg. Now she can write.”