A Win for Girls’ Sports—and Common Sense

On Tuesday, the Supreme Court answered a question that, for many, never needed to be asked in the first place: May schools reserve girls’ and women’s sports for female athletes?

For those with a basic understanding of biology and who hold to the vernacular meaning of common words, the question seems to answer itself. But progressives’ bizarre promotion of sex and gender pseudoscience over the last decade had reached such a fever pitch that the nation’s highest court needed to step in.

In West Virginia v. B.P.J., decided together with Little v. Hecox, the Court’s answer in the affirmative. Writing the majority opinion, Justice Brett Kavanaugh put it plainly: “Under Title IX and the Equal Protection Clause of the Fourteenth Amendment, may schools maintain women’s and girls’ sports for biological females? In other words, may schools determine eligibility for women’s and girls’ sports based on biological sex? The answer is yes.”

The cases involved West Virginia and Idaho passing laws that barred males from female athletic teams. The states argued that separate female-only teams exist for reasons that Title IX has always recognized: equal opportunity, competitive fairness, and, in some sports, safety. The laws did not bar transgender-identifying students from playing sports, as many news headlines would have you believe. They barred males from entering the female category.

The challengers argued that the laws discriminate on the basis of transgender status and sex, and that categorical exclusions are overly broad. Their main argument was centered around individual circumstances: B. P. J., a male student who identifies as female, had taken puberty blockers and therefore did not gain the performance-enhancing effects of testosterone before starting estrogen. The plaintiffs argued that if the point of a protected female category is fairness, then the question a state must consider is whether a particular athlete has any remaining male advantage. If testosterone has been suppressed before puberty, why exclude that male athlete?

The Court rejected that argument, holding that “Schools may determine eligibility for women’s and girls’ sports based on biological sex.” It also rejected the burdensome demand for an individualized assessment of every athlete’s body. States, the Court said, are “not required to conduct an individual-by-individual comparison of the physical and athletic capabilities of all biological males.” Furthermore, asking judges to weigh the effects of puberty blockers and hormones athlete by athlete “would be an almost impossible task for a judge to perform on an equitable basis.”

That is right as a matter of law. It is also right as a matter of biology.

The problem in the challengers’ argument is their assumption that all male athletic advantage is a result of puberty. While puberty dramatically widens the male advantage in strength, speed, power, endurance, bone size, and lung capacity, it is not the point at which the sexes stop being identical in all but their reproductive organs. Sex differences in physical performance emerge long before puberty.

Sex differentiation begins in the womb, and boys also experience a brief surge of testosterone in infancy, often called “minipuberty,” which influences later body composition and motor development. By school age, boys already tend to have more lean mass, less fat, larger hearts, and greater lung capacity. These differences are not “stereotypes.” They are physical traits directly relevant to sport.

The performance data bear this out. A 2025 study of 3,621 children ages six to 12 in a 1,600-meter race found that boys were significantly faster than girls in every grade. Large school-based fitness datasets corroborate these findings across countries and tests. Before puberty, boys outperform girls in grip strength, muscular endurance, running speed, aerobic capacity, ball throwing, and kicking distance, while girls generally outperform boys in flexibility. Exercise scientist James Nuzzo’s review of nearly 170 studies with grip-strength data from over 350,000 children in 45 countries found that boys are consistently stronger than girls at all ages.

Of course, none of this means every boy beats every girl every time. That is not how sports categories work. A heavyweight boxer can lose to a middleweight even though weight still matters enough to structure competition around it. Sports rules necessarily deal with population-level advantages.

That is why the Court was right not to make girls’ sports depend on case-by-case medical assessments. A female category cannot survive if every challenge turns into an argument over a particular individual’s testosterone levels, treatment history, pubertal stage before being administered puberty blockers, or muscle mass. The point of a sex category is to draw a clear line. The more we blur that line, the less it can serve the women and girls it was created to protect.

This decision does not impose a nationwide ban on males in women’s sports. The Court was explicit that it was not deciding whether “schools may allow biological males who identify as female to participate on girls’ and women's sports teams.” It held only that states may preserve female sports for females without violating Title IX or the Constitution.

Twenty-seven states have already done so. The remaining states should follow.