Paris Hilton has alleged she experienced "continuous torture" while attending Provo Canyon School as a teenager.
The 39-year-old socialite and DJ was sent to the school - which focuses on behavioural and mental development - for almost a year when she was 17, after she kept sneaking out to parties against the wishes of her parents.
Paris has accused the school of abuse, claiming the teachers would "scream" in her face on a daily basis.
She said: "I knew it was going to be worse than anywhere else. It was supposed to be a school, but [classes] were not the focus at all. From the moment I woke up until I went to bed, it was all day screaming in my face, yelling at me, continuous torture."
Paris also alleged the staff "bullied" her and said "terrible things" about her to her face, and even claimed there were times they would be "physically abusive".
She added: "The staff would say terrible things. They were constantly making me feel bad about myself and bully me. I think it was their goal to break us down. And they were physically abusive, hitting and strangling us. They wanted to instil fear in the kids so we'd be too scared to disobey them."
The Simple Life star had regular "panic attacks" at the school, and said she "felt like a prisoner" during her 11-month stay.
Paris claimed she was "cut off" from her parents, and was unable to tell them what was happening because the staff would "rip up" her letters.
She said: "I didn't really get to speak to my family. Maybe once every two or three months. We were cut off from the outside world. And when I tried to tell them once, I got in so much trouble I was scared to say it again. They would grab the phone or rip up letters I wrote telling me 'no one is going to believe you'. And the staff would tell the parents that the kids were lying. So my parents had no idea what was going on."
Paris left the school when she turned 18, but didn't speak about her trauma to anyone for several years.
The star opens up about her experience in her upcoming YouTube documentary This Is Paris, and says she finally feels as though her "nightmare is over".
Speaking to People magazine before the show's launch on September 14, she said: "It feels like my nightmare is over. And I'm going to watch the movie with my parents - I think it will be good for us, but emotional too. There are no more secrets."
Provo Canyon School has since responded to People magazine's request for comment, but said the school changed ownership in 2000 - a year after Paris left - so "cannot comment" on previous operations.