A. B. v. Hawaii State Dept of Educ., 30 F.4th 828

Four female student-athletes at James Campbell High School (A.B., A.M.B., T.T., A.P.) sued the Hawaii Department of Education and the Oahu Interscholastic Association under Title IX for: unequal treatment/benefits, unequal participation opportunities, and retaliation.
Plaintiffs alleged systemic sex-based disparities (no standalone girls’ locker room, inferior equipment/facilities, less pay for girls’ coaches, repeated lack of pool access for girls’ water polo) and a 6.6% participation gap between female roster spots and female enrollment.
Plaintiffs sought class certification under Fed. R. Civ. P. 23(b)(1)(B) and (b)(2) for "all present and future Campbell female students and potential students" who participate or are deterred from participating in athletics.
The district court denied class certification, holding Plaintiffs failed Rule 23(a)’s numerosity requirement (class members were geographically concentrated and identifiable) and that the retaliation claim lacked commonality/typicality (retaliation allegedly targeted the water polo team).
The Ninth Circuit granted interlocutory review, reversed the denial of certification for the unequal-treatment and unequal-participation claims (Rule 23(a)(1)), and also held the district court erred on commonality/typicality for the retaliation claim; remanded for consideration of Rule 23(b).

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether Rule 23(a)(1) numerosity is met for current female student-athletes	Class exceeds 300 current members; large size alone makes joinder impracticable for equitable relief	Joinder practicable because members are geographically concentrated and identifiable via school records	Reversed: >300 members is "large in numbers" and joinder is impracticable given logistical burdens and equitable relief sought; numerosity satisfied
Whether inclusion of "future" class members defeats numerosity	Future members make joinder more impracticable; membership turnover supports certification	Future members not reasonably identifiable, so court should disregard them in numerosity calculus	Reversed: inclusion of future members weighs in favor of impracticability; district erred in ignoring this factor and in finding no reasonable approximation of future membership
Whether retaliation claim satisfies commonality and typicality under Rule 23(a)	Retaliation against water polo had a classwide chilling effect on female athletes; motive common to all claims	Retaliation was limited to the water polo team and parents, so lacks common questions and typicality for the broader class	Reversed: under Ollier and zone-of-interests principles, retaliatory motive raises a common question and direct/indirect victims’ claims are typical; commonality and typicality satisfied

Franklin v. Gwinnett Cnty. Pub. Schs., 503 U.S. 60 (1992) (recognizes implied private right of action under Title IX)
Cannon v. University of Chicago, 441 U.S. 677 (1979) (foundational case recognizing implied private remedy under Title IX)
Mansourian v. Regents of Univ. of Cal., 602 F.3d 957 (9th Cir. 2010) (Title IX requires equivalence in availability, quality, and kinds of athletic benefits)
Ollier v. Sweetwater Union High Sch. Dist., 768 F.3d 843 (9th Cir. 2014) (permitted retaliation claims by students who suffered diminished athletic opportunities even if complaints were made by others)
Wal-Mart Stores, Inc. v. Dukes, 564 U.S. 338 (2011) (commonality requires a common contention capable of classwide resolution)
Jordan v. County of Los Angeles, 669 F.2d 1311 (9th Cir. 1982) (framework for assessing numerosity, including considering class size and practical impediments to joinder)
General Tel. Co. of the Northwest, Inc. v. EEOC, 446 U.S. 318 (1980) (numerosity inquiry is fact-specific; no absolute rules)
General Tel. Co. of the Southwest v. Falcon, 457 U.S. 147 (1982) (rejected across-the-board rule; clarified commonality/typicality analysis)
Thompson v. North American Stainless, LP, 562 U.S. 170 (2011) (third-party retaliation claim recognized under Title VII; informs Title IX zone-of-interests analysis)
Jackson v. Birmingham Bd. of Educ., 544 U.S. 167 (2005) (Title IX prohibits retaliation because it is discrimination "on the basis of sex")