In the letter, Principal Rich Kitchens describes "a 'Fantasy Slut League' 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 the letter, school staff learned about this during a recent assembly about date rape prevention.
An investigation was launched on campus and they learned this has been going on for five to six years.
The principal wrote, "Participation often involved pressure/manipulation by older students that included alcohol to impair judgment/control and social demands to be popular."
ABC7 News spoke with Superintendent Constance Hubbard about the letter.
"We wanted to make sure that parents were aware of things that were going in their kids' lives," Hubbard said.
Many parents said they were surprised to hear about the "fantasy slut league," but most didn't want to talk about it. They said Piedmont is a small town, and that is a very sensitive subject.
"I'm really glad that there's a strong administration that's willing to take on these kinds of issues; as a mother of four girls I couldn't be happier," parent Bianca Forrester said.
Piedmont school administrators say they issued the letter in an effort to be proactive.
"The main thing is that I don't want to blow this out of proportion; I don't want to make is something that is some horrible big event that we found out about," Hubbard said.
They are planning a series of on campus assemblies with lessons about preventing this in the future.