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Outcasts elsewhere, the schoolgirls chatter, compare homework and shuffle to class just like other teens but with one big difference -- all are expectant mums in South Africa's only school for pregnant girls.

This is Pretoria Hospital School where students, some as young as 13, are given the chance to carry on learning in a country where expectant schoolgirls -- and their numbers are alarming -- are often expelled.

"We offer them an environment where they can learn without being prejudiced, but that does not mean that we condone early pregnancy," said principal Rina van Niekerk.

The small establishment does not promote its service and remains low-key, amid debate over how to remedy South Africa's scholastic exclusion of pregnant teens.

"The aim of the school is to ensure that they do not miss out on education just because they are pregnant," said Van Niekerk.

She has been at the facility for 25 years, amid a lack of clear policy on pregnant learners in other state schools where treatment varies and many just shut the girls out.

Change may be afoot, however, as in July the Constitutional Court forced two state schools to end their practice of banning pregnant students from class.

Teenage pregnancy rates remain high in South Africa, despite years of campaigns against unprotected sex in a country where more than 10 percent of the population live with the HIV virus that causes AIDS.

An official study in 2002 said one in every three teenage girls in South Africa had been pregnant by the age of 19, with little apparent improvement since. The education ministry estimates that some 94,000 teenagers fell pregnant in 2011.

Poverty and other factors, like rape, have not helped .

With nearly 65,000 attacks a year, South Africa has one of the highest incidences of reported rape in the world, and the unemployment rate continues to exceed 25 percent .

The Pretoria school, in the heart of the capital, opened in the 1950s as a school for sick children in city hospitals. The first expectant girls were enrolled in the 1980s, when pregnancy out of wedlock was taboo.

It has 108 students, aged 13 to 18, following a peak in 2011 with 134 girls. After giving birth, the teens return to finish the academic year as new mothers.

Van Niekerk is protective of her students, who playfully pat each others tummies under the blue uniforms. She is adamant that pregnant learners pose special challenges.

"Some girls have trouble concentrating and they sometimes suffer from pregnancy related sickness," she said. "We have to be really patient sometimes."

Not all agree, like Andile Dube, the director of LoveLife, South Africa's largest youth-targeted HIV/AIDS campaign.

She is opposed to the idea of exclusive schooling for pregnant girls, saying it does not provide a solution to the country's vast problem.

"I think it only deals with pregnancy management rather than prevention," she told AFP.

"I'm of the view that if you start to create those schools around the country, you are almost saying pregnancy is a condition that is actually very exclusive, it's something that has to be treated differently," she said.

The learners at Pretoria themselves are positive.

Naledi Vuma, an 18-year-old who gave birth last year, said she was grateful to continue classes while expecting and then return to complete her studies. Being among other pregnant girls helped her "feel comfortable", she said.

According to 2012 figures by the World Health Organisation, there are 16 million adolescent pregnancies around the world and 95 percent of these occur in developing countries.