U.S. talk show host and media magnate Oprah Winfrey said on Monday she was “cleaning house” at her exclusive all-girl academy in South Africa after a dormitory matron was charged with abusing students.

Describing the charges — including soliciting under-age girls to perform indecent acts — as one of the most devastating experiences in her life, Winfrey said she had not renewed the head mistress’s contract and was taking other tough measures.

“We are removing the dorm parents, and as I have said to the girls, (we are) cleaning house from top to bottom,” she said in a video news conference from Chicago.

“It has shaken me to my core,” said Winfrey, who has herself told of suffering sexual abuse as a child and offered advice to other victims.

Former dormitory matron Virginia Mokgobo, 27, was arrested on Thursday on charges including assault, indecent assault and soliciting under-age girls to perform indecent acts.