The head mistress at Oprah Winfrey‘s school in South Africa has pleaded not guilty to charges of abusing students.

Virginia Mokgobo, 28, who ran the Oprah Winfrey Leadership Academy near Johannesburg, was arrested in 2007 after six teenage alleged victims swore a complaint.

Mokgobo was charged with assault, indecent assault and soliciting under-age girls to perform indecent acts.

Oprah pledged to build the academy after a meeting with Nelson Mandela six years ago and personally interviewed many of the students who came from low income families.

The school opened in 2007 at a cost of $40 million.

Oprah praised the students who came forward, "My experience with child predators is that no one ever, ever abuses just one child."