Oct. 23, 2012 -- A top-tier California high school informed parents of a "Fantasy Slut League" in which male students "drafted" female students and earned points for sexual encounters.

The sex game was brought to the attention of officials at Piedmont High School in Piedmont, Calif., who launched an investigation earlier this month. The school is known for ranking in the top handful of the state's schools in standardized tests.

In a letter to parents, Principal Rich Kitchens described a ritual "in which our female students (unbeknownst to most of them) are drafted as part of the league...Male students earn points for documented engagement in sexual activities with female students," according to ABC News affiliate KGO-TV.

Many students, both male and female, knew about the league and participated either willingly or because of social pressures, Kitchens wrote.

The principal said the "league" revolved around varsity team players and had been around for years.

"The revelation that students expressed concern that the fallout could result in discipline and affect their college applications suggests an understanding by students that there is something wrong with the 'Fantasy Slut League,'" Kitchens wrote in the letter.

The Piedmont High School and officials from the school's district did not return ABC News' phone calls and messages.

The school is planning assemblies and hopes the letter will create a discussion, assistant superintendent Randall Booker told KGO.

"It always comes back to how do we educate students and to have further conversations with the community," he said.