Mandelzis’s lawyer, Iliana Konidaris, told me that the existence of these mixed-gender-competition guidelines in New York has effects beyond the playing field. “The sports field is not … a niche issue,” she said. “It’s where a lot of students get their sense of fairness, sportsmanship, equality, culture, and confidence.” This became starkly clear to Musto, the University of British Columbia researcher, when she recently spent months observing sixth, seventh, and eighth graders at a school in California to assess how gender informs education. The gender binary’s influence on school kids crystallized for her when she interviewed nearly 200 students and the one subject they commonly identified as a “boys’ subject” was P.E.