A workshop about homophobic and transphobic bullying, which was due to take place at a secondary school in Dublin, was postponed after parents raised concerns.
The talk was due to be held today with Transition Year students at Coláiste Eoin by the group Shout Out.
However, the organisers this morning were told it would not be going ahead.
It said it was told that the parents and the board felt "the other side needed to be heard".
The group said it tried to contact the school further as to what the exact reason was, but it had been told the school would not be commenting.
Speaking this afternoon, the school's principal Finín Máirtín said the workshop had not been cancelled but had been postponed.
He said that parents had received late notification about the talk, because letters had only gone out yesterday.
Some parents, he said, had not received letters and some had a difficulty with the topic of LGBT issues being raised at the workshop.
The reason the talk had been postponed was to allow the school to notify parents more fully about the workshop, he said.
Mr Máirtín later said he did not intend "the other side" comment to mean homophobic bullying as opposed to anti-homophobic bullying.
He said he meant to say viewpoints that parents felt might not have been expressed.
In a statement tonight, the Board of Management said Shout Out had made presentations to the school in recent years and no issues had arisen.
However after parents outlined concerns this week, it said it was "incumbent on the Board to address all issues and to seek the advice available from Catholic management representative bodies available to secondary schools".
It said it was at all times made clear that the workshop was not being cancelled.
Shout Out said it has worked with the school twice before and said it hoped it could work with them again.