I was warned by one Vlakfontein teacher not to arrive during lesson times, when knife-wielding gangs might prey on isolated visitors. Most pupils at the state school in Mamelodi township - situated east of Tshwane, formerly Pretoria, apartheid’s model city - cannot afford the paltry 250 rand (pound;20) in annual fees, and the school has been plagued by violent attacks in recent years.

Moses Masia, 30, a maths and science teacher, says gangs climb over the school fence armed with guns. Teachers have been robbed of money and mobile phones. But government rules that make expulsion from school difficult have given unruly pupils the upper hand: one boy tried to stab a teacher he was arguing with but was held back.

“The learners can get away with murder,” said Mr Masia. “We find them bringing drugs into school. Some bring knives and even guns.”

St Alban’s, by contrast, would not look out of place in Surrey. It is a well-furnished school set in leafy parkland. It is one of the country’s top 10 boys’ independents, situated on the outskirts of the capital. The fees are R48,000 (pound;3,800) for day scholars, manners are impeccable and expectations are high.

Yet Vlakfontein is benefiting from a remarkable partnership between the wealthy Anglican independent and local state schools struggling to cope with scant resources, as much a product of the country’s political history as its lack of development.

Four days a week, buses collect 360 nine to 14-year-olds from surrounding township schools for extra lessons in English, the language of instruction for the “matric”, and 160 grade 12 pupils (aged 17-19) for extra tuition in English, maths and science. Up to three times a year at weekends teachers are bused in for training in key subjects.

I met Mr Masia while he was at a training workshop on teaching problem-solving in maths. The outreach programme, now sponsored by gold and diamond mining firms Anglo American and De Beers, was set up by Don MacRobert, the “Robben Island lawyer” who represented many of the anti-apartheid leaders imprisoned with Nelson Mandela.

As chairman of the college’s council, in 1981 he urged the school to take a lead in sharing its resources and offer assisted places to black children in defiance of threats of closure from the apartheid regime. Within four years, most Anglican schools had followed suit.

South Africa’s education system is still troubled and grossly divided along racial lines, according to Graeme Bloch, education policy analyst at the Development Bank of South Africa.

A government survey shows that only 0.1 per cent of schools in black areas are operating at an international standard, compared with 60 per cent of schools in white areas.

Alongside a lack of facilities and experienced teachers in black schools (many staff were moved into better-paid government jobs when apartheid collapsed) there are also 11 official languages, making the question of which to teach in complex. Maths and science teaching in black areas is also particularly poor, said Mr Bloch while violence is a persistent problem.

But the training workshops at St Alban’s have given Mr Masia hope that he can motivate disaffected learners, despite classes of up to 80 children.

Last year, 82 per cent of the grade 12 outreach pupils passed their matric.

Mr Masia knows the impact that St Alban’s will have made on those pupils.

Without the outreach programme, he might never have passed his matric and made it into teaching himself.

“I first came here in 1993 to learn about maths and computers,” he said.

“This is my mentor school.”

Dania Vieyra, co-ordinator of St Alban’s maths workshops, said: “We’ve been working in outreach for a very long time. If you live in Africa and you don’t do it, you don’t deserve to be there.”

Additional research by Jody Sabral