The American Civil Liberties Union (ACLU) has set Friday 3 May as the deadline for a Pennsylvania school to apologise for having listed a trans student on a ‘prom queen’ ballot, when he had campaigned to be ‘prom king’.

Issak Wolfe, a trans student who identifies as male, became part of a prom controversy after his principal placed him on the ballot for prom queen, switching at the last moment after Wolfe had campaigned to be prom king.

Wolfe had said he would like an apology from principal Mark Shue for the “degrading” incident, while his girlfriend, Taylor Thomas, started a petition to get Wolfe named prom king.

The York Dispatch reports that Mr Shue threatened to bar Thomas from attending the prom after she made critical comments about his treatment of Wolfe on Facebook. However, the school district announced on 26 April that she would be allowed to attend the prom, which took place on Saturday, with Wolfe.

Although Wolfe’s father, William Stambaugh, said the event “went off really well”, the ACLU says there is still an apology to be made.

A letter sent by the ACLU on 26 April demands an apology within one week, with the potential for future legal action.

“There’s very clear liability for the school district,” said the ACLU’s Molly Tack-Hooper.

The letter also demands a guarantee that Wolfe will be able to wear the black cap and gown worn by male students at graduation, as opposed to the yellow one worn by females, and be announced as Issak Wolfe.

Although his school diploma will carry his birth name, Sierra Stambaugh, as he has not yet legally changed it, Wolfe said being treated as a man in every other respect was significant.

“It’s embarrassing at this point in my life to have my name read as the wrong name,” Wolfe said. “I don’t want to be forced to wear yellow because I’m not a girl. My family and I both want this so they can remember it the right way.”

Neither Mr Shue nor Red Lion High’s superintendent, Scott Deisley, have commented on the incident.

In March a high school student from Georgia filed a federal lawsuit against his school, alleging that the administrators removed him as student body president, after he proposed to make the prom more inclusive to LGBT students.

In 2010 student Constance McMillen became a figurehead for LGBT-inclusiveness after a long conflict with her school over her right to take her girlfriend to prom.