At the end of each school year, when she says goodbye and wishes her students success in high school, Martha Mohulo can't help but worry. A veteran primary school teacher in Soweto, she knows the dangers lurking in this sprawling, struggling township – perils such as violence, AIDS, and teenage pregnancy.

So when Oprah Winfrey picked eight of Ms. Mahulo's students to attend her lavish new girls' academy south of Johannesburg, the teacher was thrilled.

"Those girls who went to Oprah, they are going to be safe," Mohulo says. "They are much better off."

Ms. Winfrey's school, a $40 million project that opened Tuesday, is one of the most recent and high-profile projects in a growing worldwide campaign to improve girls' education. Such female-focused aid yields perhaps the highest dividends for developing nations, say experts, though they are quick to point out that boys face challenges as well.

"I think it's very important for people to recognize that the lack of education for both boys and girls is a crisis in Africa," says Gene Sperling, director of the Center for Universal Education at the Council on Foreign Relations. "But the benefits of girls' education, in terms of improving health, women's empowerment, and family well-being, probably does make girls' education the highest-returning social investment in the world."

The World Bank has found that when a country improves education for girls, its overall per capita income increases and its fertility rate drops. Other studies show that improved female education is linked to higher crop yields, lower HIV infection rates, and reduced infant mortality. UNICEF's annual "State of the World's Children Report" calls gender equity – particularly in education – a "double dividend" for developing countries.

"With education, the girl child will grow up and be a better mother – she will be better able to understand the importance of her own children being educated, and will be better able to provide for her children," says Sarah Crowe, a spokesperson for UNICEF in Johannesburg. "Men and boys are often out of the home," she notes, so that fathers are less able to teach their children what they have learned.

Why African girls don't stay in school

Less than half of southern Africa's girls complete primary school (46 percent, compared with 56 percent for boys), while 26 percent enroll in secondary school (33 percent for boys). Though the statistics for boys are hardly uplifting – 44 million aged six to 11 are denied an education, compared with 60 million girls – girls have long faced more barriers to education than boys.

The reasons are myriad. In urban areas, pregnancy and poverty limit educational access. In rural regions, poor families need girls to help in the fields. When a financially strapped family must chose between sending a son or daughter to school, cultural norms favor the boy. And across southern Africa, when relatives fall ill from AIDS, girls are the ones who stay home to give care.

Governments and international agencies have recognized this, and are working towards solutions. The UN Millennium Development Goals call for both gender equity and universal primary education by 2015. Many African governments have recently eliminated primary school fees, which have hampered girls' enrollment.

Now, the challenge is to secure long-term funding, to hire and train enough teachers to manage millions of new students, and to make sure educational quality goes along with access, researchers and aid groups say. Advocates are also pushing for free secondary education, which they say will further increase girls' literacy.

David Archer, the head of international education for ActionAid, a nonprofit development group, says he is seeing a new interest in global education from private philanthropies, as well. Over the past year or so, he says, some two dozen American philanthropies have started international education projects. Last month, the Bill and Melinda Gates Foundation and the William and Flora Hewlett Foundation announced a $60 million effort to improve education in South Asia and sub-Saharan Africa.

Winfrey school: Vanity project or shining light?

The Oprah Winfrey Leadership Academy for Girls, set on 52 manicured acres in the village of Henley-on-Klip, has state-of-the-art classrooms and laboratories, a 600-seat theater, a library, beauty salon, yoga studio, and Oprah-decorated dorm rooms. This year, 152 seventh and eighth graders will attend the school; next year, Winfrey says, it will hold 450 students in Grades 7 to 12.

Some education advocates have criticized Winfrey's academy as a "vanity project," and say her $40 million could have been more widely and smartly distributed, while others say that she's managed to raise more popular attention than has any NGO.

"This school is ... shining a spotlight on girls' education in Africa," says Mr. Sperling, who also served as national economic adviser to President Clinton. "Five years from now, when people see some of these young women on her show just blowing you away, it is going to be a powerful symbol of what the potential of the poorest girls in Africa really is with the same type of educational opportunities that so many of us were lucky enough to be born into."

Mr. Archer, however, cringes at Winfrey's project. "I felt very uncomfortable about it," he says. "It's something where she can have direct control and direct engagement, rather than doing the more important and less personalized work. That same amount of money could improve the quality of schools no end throughout entire districts and provinces."

But Winfrey and her supporters defend her targeted largess. "I think the government has to be very focused on spreading resources evenly," says Sperling. "But I think there's nothing wrong, and a lot right, with a private individual saying, 'I want to do something terrific to give some of the most underprivileged girls in the world the opportunity to be leaders.' You need both."

The girls who attend her academy, Winfrey says, will become Africa's next leaders. "I know that this Academy will change the trajectory of these girls' lives," Winfrey said in a statement this week. "They will excel and pass their excellence on to their families, their nation, and our world."