Free primary school education is now universal in Kenya. However, there are few public schools in Nairobi's teeming slums, leaving thousands of children squeezed out of the formal education system. Non-formal schools have sprung up to fill the gap, but these are largely underfunded and understaffed.

It is lunch time at St. Christines Community Centre. Children line up to receive their mid-day meal.

This might be the only meal they have for the day. They come from Kibera slum, one of the largest in Africa, where the average family survives on less than one dollar a day. Kibera and other slums in the capital Nairobi lack most basic services, including education.

Susan Munuhe is assistant director of education in the Ministry of Education. She describes the situation in one Nairobi slum, Mathare.

"The public primary schools near Mathari slum, they are about three and they can only cater for a maximum of 2,000 children, and yet Mathari slum alone has about over 300,000 school-age-going children," she said.

To fill in this gap, dozens of non-formal schools such as St. Christines have sprung up in Nairobi's slums.

These schools teach the formal, national curriculum but largely operate without trained teachers and inadequate resources.

Country-wide, there are 235,000 trained school teachers registered at the Teachers Service Commission (TSC) who teach in the formal education system.

Officials say most teachers in non-formal schools have not received teacher training, and are not members of the TSC.

Charles Ochieng Ochiel is director and founder of St. Christines Community Centre.

"If we can get teachers from the TSC or we can be able to pay those teachers who are from college, then quality [education] will be there," he said.

Education activists say there is almost no follow-up by the Ministry of Education of the quality of teaching and other aspects of education in informal schools.

Don Bonyo is programs manager with Daraja Civic Initiatives Forum, an educational group.

"We have not seen the schemes of work being inspected. We have not seen the lessons - they make lesson notes - being inspected. We have not seen examination records being inspected," he said.

Most non-formal schools also lack the necessary amount of books and other school supplies.

Ministry of Education official Susan Munuhe says only about 200 non-formal schools across the country receive funds for the purchase of instructional materials under the government's free primary education program.

There are at least 1,600 informal schools in Kenya according to education activists.

Diana Atieno Tujuh is a volunteer pre-primary teacher at St. Christines Community Centre.

She says the government had only supplied books to students once within the past few years.

"All of them were given but it was only once," she said.  "So right now they do not have books, they have to buy them. Some parents have a problem in buying the books. At times the teachers have to sacrifice and buy the kids some books."

She says many students are sleepy or otherwise unable to concentrate in class because there is not enough food to eat at home.

Education activists argue that the presence of non-formal schools sets up a two-tiered system, where those children living outside of slums get a better quality education.

Government spokesman Alfred Mutua says that every child in Kenya has access to the same education.

Mutua says the government is trying to discourage informal schools, as he says there is no gap to be filled by those schools and that the government has never turned away a child from a public school. He says that the government is building more schools, but it will take time.