English School Mandates Trousers for All Students
The rationales: avoiding short skirts, and making things easier for transgender students.
Priory School in Lewes, East Sussex, made trousers compulsory for new and existing students for the new term.
The school said "concerns" had been raised over the length of girls' skirts and new rules also catered for a handful of transgender pupils.
As best I can tell, the school is a government-funded school that's something like what some American states call a "charter school"; despite the name, it doesn't seem to be a religious school or what Americans would call a private school.
Unisex uniform policies are of course not unheard of, for instance in police departments or in the military. Pants are sometimes required for safety reasons; and, more broadly, rigid uniform requirements are sometimes imposed in paramilitary organizations (such as the police) for "morale and esprit de corps, and public confidence." But my sense is that such requirements are on balance fairly unusual, even in institutions (such as schools) that have uniforms. And I think they're hard to justify when there's no real safety need, and when they're not a condition of a government paycheck needed to improve the employee's effectiveness.