One school principal says people would be 'appalled' if the idea of single-sex schools was implemented today.
Simon Lewis, principal of Carlow Educate Together National School, was speaking as the Government is being urged to end single-sex schools within the next 15 years.
Labour's Aodhán Ó Ríordáin says co-ed schooling is already 'de facto' policy, and his party now wants a timeline put in place to phase out single-sex schooling entirely.
Labour is publishing a bill this week which aims to bring an end to gender discrimination in school admission.
Mr Lewis told The Hard Shoulder Ireland is an outlier on this.
"Co-ed schools are - I guess normal is the only word I can use - and single-sex schools are just abnormal internationally.
"So he's absolutely got then right idea."
But he disagrees with a suggestion that there is a toxic masculinity in all-boys' schools.
"I just don't think that's fair - I never went to a boys school, but many of my friends went to these schools.
"And I can't say any of them would be described as suffering from toxic masculinity.
"Obviously it's a really good idea for Ireland to move towards a co-educational system, we have to be doing it for the right reasons.
"And I suppose linking it to toxic masculinity, I just think isn't fair and was a stretch too far".
And he says this is not as much about academic outcomes as other issues.
"Our educational outcomes seem to be quite similar whether we're single-sex or not.
"The problem comes down to outside of educational outcomes, and I think that's possibly more problematic.
"So you might do just as well in a single-sex school as you would in a mixed school, but - for example - a child who may be identifying as a different gender is definitely going to suffer in a single-sex school."
Mr Lewis believes if the suggestion of single-sex schools was made today, "I think people would be appalled.
"But just because it's so normal for us we just seem to accept it.
"And when we look at Ireland internationally, we're so far removed from everywhere else... it just makes no sense to have it."
Put to him that the reason for many single-sex environments is linked to the nature of the religious background of the schools, he believes this needs to change.
"It's absolutely something that I would believe needs to change as well - and I don't think it's anymore complex really than the single-sex issue.
"Effectively when we have single-sex schools we discriminate on the basis of gender.
"And if we have denominational schools, we discriminate on the basis of religion.
"The very reason that I have to teach in an Educate Together school is because I'm not from a Christian background.
"Therefore I can't work in a Christian school because employment law would, I suppose, put me in a situation where I'd be vulnerable from discipline because of an accident at birth.
"But children have to go through this every day".