This photo provided by Focus Features, shows actors Heath Ledger, left, and Jake Gyllenhaal, who play two cowboys from very different backgrounds who meet and fall in love, in a scene from 'Brokeback Mountain.[AP]

CHICAGO - A girl and her grandparents have sued the Chicago Board of Education, alleging that a substitute teacher showed the R-rated film "Brokeback Mountain" in class.

The lawsuit claims that Jessica Turner, 12, suffered psychological distress after viewing the movie in her 8th grade class at Ashburn Community Elementary School last year.

The film, which won three Oscars, depicts two cowboys who conceal their homosexual affair.

Turner and her grandparents, Kenneth and LaVerne Richardson, are seeking around $500,000 in damages.

"It is very important to me that my children not be exposed to this," said Kenneth Richardson, Turner's guardian. "The teacher knew she was not supposed to do this."

According to the lawsuit filed Friday in Cook County Circuit Court, the video was shown without permission from the students' parents and guardians.

The lawsuit also names Ashburn Principal Jewel Diaz and a substitute teacher, referred to as "Ms. Buford."

The substitute asked a student to shut the classroom door at the West Side school, saying: "What happens in Ms. Buford's class stays in Ms. Buford's class," according to the lawsuit.

Richardson said his granddaughter was traumatized by the movie and had to undergo psychological treatment and counseling.

In 2005, Richardson complained to school administrators about reading material that he said included curse words.

"This was the last straw," he said. "I feel the lawsuit was necessary because of the warning I had already given them on the literature they were giving out to children to read. I told them it was against our faith."

Messages left over the weekend with CPS officials were not immediately returned.