8:17 AM PT -- Officials at the Provo Canyon School tell TMZ it was sold by previous ownership in August 2000, so ... "We therefore cannot comment on the operations or patient experience prior to this time."
We're told the school today is a psychiatric youth residential treatment center for kids with special mental health needs, focused on "providing effective treatment, compassionate care and a nurturing environment for the students and families we serve."
Paris Hilton's opening up about a traumatic chapter of her life before her 'Simple Life' stardom ... in an upcoming documentary that's pretty shocking.
The famous heiress describes how her rebellious youth living with her family in NYC's Waldorf Astoria hotel resulted in her parents sending her to several boarding schools ... the last of which was Utah's Provo Canyon School.
Paris stayed there for 11 months before turning 18, but says it was less of a school and more of an obedience boot camp where it was "all day screaming in my face, yelling at me, continuous torture."
She alleges the abuse was verbal, mental and emotional -- claiming the staff would say terrible things to her, try to make her feel bad and bully her -- but also claims there was physical abuse ... hitting and strangling the kids.
Paris says students could end up in solitary confinement for up to 20 hours a day, and she was having frequent panic attacks and crying daily due to the fear and misery. She says ... "I felt like a prisoner and I hated life."
Three of her classmates also appear in the upcoming documentary, "This is Paris," adding more allegations of abuse ... including being force-fed medication.
Paris was freed from the boarding school when she turned 18 in 1999, and says she just wanted to put it behind her so badly she never really talked about it ... even to her parents.
She says she was ashamed of the time there and adds ... "I buried my truth for so long."
The documentary premieres September, 14 on YouTube.