A group of students and parents from Minnesota filed a lawsuit Wednesday against the federal government and their school district for allowing a transgender student who was born male but identifies as female into the girls’ locker rooms, showers, and restrooms. The lawsuit is the latest in a series of challenges to the Obama administration’s bathroom mandate issued in May that requires public schools and universities nationwide to give transgender students full access to school facilities based on their gender identity instead of their biological sex. Schools that do not comply with the administration’s guidance could face legal action or...