Tearing up, US talk show queen Oprah Winfrey said Friday she is proud of the first graduates from her South African girls' academy and that the scandals the school has faced have only made them stronger.

Five years after its founding, the Oprah Winfrey Leadership Academy for Girls will graduate its first class of 72 young women Saturday.

Winfrey said the day will be a return on her $40-million investment to build the school for disadvantaged girls, a project she undertook with the encouragement of South Africa's first black president, Nelson Mandela.

"The reward for me is what's going to happen tomorrow when each one of those girls walks across the stage. Each one of those girls walking across the stage represents a life born of freedom, the end of apartheid, that is able to now break the cycle of poverty in her family," she told AFP.

"That really fulfills Madiba's dream, and also fulfills my own," she said, using the clan name by which Mandela is affectionately known.

In a story that could have featured on Oprah's own long-running talk show, whose last episode aired in May after 25 years, the graduating class has had to overcome its share of trauma to reach the pinnacle.

The year the academy opened, it was rocked by allegations that a dormitory matron sexually abused some of the girls. The matron was arrested and charged but later acquitted, a decision Oprah called disappointing.

"I still believe the girls and will always believe the girls," she said Friday.

The school was also rocked last year by reports that a dead baby had been found in a student's bag after she was hospitalised for excessive bleeding.

Winfrey, whose own rise to the status of talk show superstar and billionaire followed an impoverished childhood scarred by sexual abuse and a teen pregnancy, said she knew from her own experience that the girls would emerge stronger from the episodes.

"For me, the experience of child abuse as a child created a greater sense of empathy and strength for me to be able to deal with it when it occurred in this school. For me, the experience of being a 14-year-old girl hiding a pregnancy gave me the strength and the empathy to deal with it (here)," she said.

"It strengthened us," she added.

"These girls are going to amaze you.

"They've already been through more traumas than most people face in a lifetime. And every trauma, every difficulty, that occurs in your life that doesn't take you down, it strengthens you."

Winfrey, who gave each girl a cell phone with her number programmed into it after the matron abuse scandal, said she has developed an intensely personal relationship with the first batch of grads.

"Particularly for this first class and the second class, these girls were hand-picked by me and I know every single girl by name," she said.

"It's more than a personal relationship. These are my daughters."

The first class achieved a 100 percent pass rate on its end-of-year exams. Two of the girls plan to go to university in the United States, eight in other foreign countries and 62 in South Africa.

"We have proven that you can take girls out of completely traumatised, difficult circumstances -- literally carrying buckets of water on their head and bathing in the river -- and turn them into some of the most powerful people in the world," Winfrey said.