EXCLUSIVE — A top women’s sports advocacy group is pushing a Nevada county school district to adopt measures that would block transgender athletes from participating in women’s sports by creating a category specifically for biological females.

In a letter sent to the Washoe County schools, the Independent Council on Women’s Sports urged administrators to “take decisive action” and implement new policies that ensure “fair competition and compliance with Title IX.” The letter comes in response to recent reports of biological males who identify as females participating in women’s sports, which the group argues is a risk to athlete safety and may lead to sex-based harassment.