Principal of Presentation College Carlow Ray Murray has described comments on social media about the school as scandalous and damaging to staff.
Mr Murray said it was untrue that female students were asked not to wear leggings or tight tracksuit bottoms.
He said that staff had only reminded students at assemblies to abide by the school dress code and wear the PE uniform properly.
Mr Murray said he had spoken to students with concerns and to scotch the unsubstantiated claims that had been made and put their minds at ease.
It comes as more than 5,000 people signed a petition criticising the secondary school after it was reported that female students were told not to wear tight clothing.
Dozens of parents of students attending Presentation College Carlow expressed their anger on social media.
Mr Murray said today that nothing "inappropriate, wrong or uncomfortable" was said to female students in a school assembly about uniform regulations, although he accepted some students were upset afterwards.
Speaking on RTÉ's Morning Ireland, Mr Murray said that the school's uniform regulations "had not changed at all", despite reports to the contrary.
He said that he is "bemused and annoyed" about some "scandalous comments" on social media, which he said were damaging to staff.
Mr Murray explained that he and other members of staff had noticed that on PE days when the students can wear PE gear that students, particularly the girls, were not following the school regulations and "it was becoming more of a fashion show" than anything else.
It was decided to hold assemblies to give students "a reminder of what the full school regulations about uniform are".
Mr Murray said the boys were not spoken to as the issue was primarily with the girls and he defended this decision, saying space was limited and also that the teaching staff did not want to embarrass the girls.
He said their PE uniform was not being worn properly, as instead of tracksuits some were wearing "a variety of garments, particularly leggings".
The principal said no remark was made about teachers being uncomfortable with what the girls were wearing and that the notion that it was said that "girls cannot wear leggings because ... " was wrong.
"If a wrong message came through, obviously we do not want that to happen and I have an open-door policy for talking to the kids," he said.
Mr Murray said he had rang some parents to clarify what happened and allay any concerns, as well as talking to individuals who were upset.
He said that people would not want to come to the school if there was an ethos of "body shaming girls" and, he said, he feels for staff who have "taken the brunt of unsubstantiated rumour" on social media.