In November 2016, Britain’s High Court ruled that sex segregation in religious schools is not discriminatory per se, and is allowed as long as girls and boys receive education of equal quality. This decision was reversed by the Court of Appeals (CoA) in October 2017. We assert that the Court was not bound to accept Ofsted’s position only if it found that ‘separate cannot be equal’, critique both courts’ position on a number of fronts, and argue that they asked the wrong questions. The High Court was too quick to reject, and the CoA too quick to deem as irrelevant, the similarities between race segregation (deemed inherently unequal) and sex segregation (which is not). The CoA’s reluctance to consider the group implications, and to focus solely on the individual boy or girl. The High Court and the majority in the CoA were wrong to dismiss the claim that segregation on the basis of sex constitutes expressive harm to women in general. In the context of religious schools, we suggest that gender segregation conveys a message of inferiority, suggesting that girls’ (and women’s) presence in the male-dominated public sphere is unwelcome, and that it preserves traditional gender roles thereby curtailing girls’ opportunities. We acknowledge that religious communities may genuinely feel obligated to instil gender segregation in education and elsewhere. We examine whether religious or pedagogical considerations may override the argument against gender segregation, and whether institutional questions (e.g. if the school is private or public or if it is publicly funded) make a difference in this respect, issues not addressed by the courts.