Students were told not to wear tight-fit clothing in PE as it could be distracting to staff.
Almost 5,000 people have signed an online petition, amid a backlash against the demand.
Labour's education spokesman, Aodhán Ó Ríordáin, says students and parents are right to be disgusted:
"I think the school has to apologise to the student body. I think what happened was extremely unfortunate. I think it goes to the heart of many conversations and debates that are happening about second level education and the manner in which it is run. I think the statement made by whoever made the statements was particularly unfair to the students. It's sexualises young women and young girls in a completely inappropriate manner."
