The former headmistress of Oprah Winfrey's school for disadvantaged girls has denied being aware of allegations that a dormitory matron sexually assaulted and abused pupils.

Winfrey announced Monday that Nomvuyo Mzamane's contract would not be renewed, indicating that school officials had ignored complaints from the girls and tried to keep allegations of abuse from her.

"Contrary to reports, I had no knowledge of abuse. I did not and would never participate in any such cover up," Mzamane said in a statement issued Thursday through her U.S.-based lawyer.

Mzamane was suspended last month when allegations of abuse by one of the dormitory matrons surfaced.

Tiny Virginia Makopo, 27, faces 13 charges of indecent assault, assault and criminal injury committed against at least six students aged 13-15 and a 23-year-old at the school. Makopo, who said she was innocent, was freed on bail Monday.

Winfrey, who was a victim of child abuse herself, promised an overhaul of the school and said she had apologized to parents.

Winfrey opened her Leadership Academy for Girls outside Johannesburg on Jan. 2, with celebrities including Tina Turner and Spike Lee in attendance, as well as former President Nelson Mandela.

The lavish $40 million school was the fulfillment of a promise she made to Mandela six years ago, and aims to give girls from deprived backgrounds a quality education in a country where schools are struggling to overcome the legacy of apartheid.