CHICAGO — Asked to call a transgender boy by a male name he has chosen for himself, teachers and administrators around the country have leaned toward a simple response: Sure. Allow a high school student who was born male but identifies as female to join the volleyball team? Fine.

But as transgender students assert themselves more, schools have hesitated at the locker room and the bathroom. Many have developed policies that require transgender students to use private changing and showering facilities, drawing opposition from these students, their parents and advocates who say the rules are discriminatory.

The Education Department on Monday gave school officials at a suburban Chicago high school 30 days to resolve a dispute with a transgender student who identifies as a girl and has sought to change and shower in the girls’ locker room without restrictions; otherwise, the school risks forfeiting Title IX funding. The confrontation was an echo of battles nationwide, where the locker room and often the restroom are the stage for a fierce fight over how extensively transgender students should be accommodated.

“I think it’s an issue that people are thinking about a lot,” said Thad Ballard, the president of the Elko County school board in northeast Nevada, which voted in September to keep transgender students out of bathrooms and locker rooms that correspond with their gender identity. He said the move was intended to preserve “the centuries-long tradition of respecting the difference in the sexes.”