other types of interscholastic, club or intramural athletics. We give Chevron deference to this regulation. See note 5, supra. See also McCormick ex rel. McCormick v. School Dist. of Mamaroneck, 370 F.3d 275, 300 (2d Cir. 2004) (applying three-part test to high school districts); Horner v. Ky. High Sch. Athletic Ass’n, 43 F.3d 265, 272–75 (6th Cir. 1994) (same).
B
In 1996, the Department of Education clarified that our analysis under the first prong of the Title IX “effective accommodation” test—that is, our analysis of whether “participation opportunities for male and female students are provided in numbers substantially proportionate to their respective enrollments,” 44 Fed. Reg. at 71,418—“begins with a determination of the number of participation opportunities afforded to male and female athletes.” Office of Civil Rights, U.S. Dep’t of Educ., Clarification of Intercollegiate Athletics Policy Guidance: The Three-Part Test (Jan. 16, 1996) (“1996 Clarification”). In making this determination, we count only “actual athletes,” not “unfilled slots,” because Title IX participation opportunities are “real, not illusory.” Letter from Norma V. Cantú, Assistant Sec’y for Civil Rights, Office of Civil Rights, U.S. Dep’t of Educ., to Colleagues (Jan. 16, 1996) (“1996 Letter”).
The second step of our analysis under the first prong of the three-prong test is to consider whether the number of participation opportunities—i.e., athletes—is substantially proportionate to each sex’s enrollment. See 1996 Clarification; see also Biediger v. Quinnipiac Univ., 691 F.3d 85, 94 (2d Cir. 2012). Exact proportionality is not required, and there is no “magic number at which substantial
