JOHANNESBURG, South Africa (AP) ¿ Oprah Winfrey said yesterday she wept after hearing that a dormitory matron at her academy for disadvantaged girls was accused of abusing students, and said school officials hid the facts of the case and told the girls to "put on happy faces''.

Though she said she was not responsible for hiring at the school, Winfrey said the screening process was inadequate and "the buck always stops with me''. She said the head mistress' contract would not be renewed and promised a shake-up.

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.

She was freed on bail yesterday.

"When I first heard about it I spent about a half-hour going around my house crying," Winfrey said at a news conference. She said learning about the allegations was "one of most devastating experiences of my life''.

Makopo said she was innocent when the charges were read during a bail hearing in Johannesburg, and the magistrate allowed her to go free on a bond of $450. Makopo, who was arrested on Thursday, was not asked to enter a formal plea.

Winfrey said she was initially told a girl who accused the matron of abuse had left the school because the girl's mother wanted to spend more time with her.

She said girls at the school, which she visited frequently, told her they were instructed "to put on happy faces" when she was there and not complain.

Winfrey, who has in the past spoken of the abuse she suffered as a child and campaigned for laws in the United States to protect children from abusers, said that because of the high rates of rape and sexual abuse in South Africa, she had worked to ensure outsiders would not be able to reach students at the school.

But "as often is the case, child abuse, sexual abuse happens right within the family, right within the confines of people you know," she said.

Winfrey has spoken in the past of being raped by a distant cousin at age nine and then abused by three other men, trusted family friends.

The school announced on October 17 that a dormitory matron had been suspended amid allegations of serious misconduct. The Oprah Winfrey Leadership Academy for Girls said private US and South African detectives were investigating, as well as South African police.

Makopo, who twisted her braids nervously and blinked back tears at yesterday's court hearing, said she was "not guilty" after the charges were read.

Shortly after Makopo was freed on bail, Winfrey answered reporters' questions in South Africa through a satellite link teleconference from the United States.

Winfrey opened her Leadership Academy for Girls outside Johannesburg on January 2, with celebrities such as 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 152 girls from deprived backgrounds a quality education in a country where schools are struggling to overcome the legacy of apartheid.

"What I know is that no one ¿ not the accused nor any persons ¿ can destroy the dream that I have held and the dream that each girl continues to hold for herself at the school," Winfrey said.