For 190 years Deerpark CBS, on the southside of Cork city, was a boys-only secondary school.
Just over two years ago that all changed when the first girls stepped through the main door.
"It is the best move we ever made," said principal Aaron Wolfe. "No question."
The change was prompted by a primary school pupil – Megan Hurley – who wrote to the school, urging it to admit girls.
She was attending a mixed primary and had no co-educational secondary school option in the area.
"When we consulted parents, staff, students and the patron body – the Edmund Rice Schools Trust – there was huge support for it. It was clear, looking at the demographics, that a mixed school was needed."
The school changed its name to Coláiste Éamann Rís, introduced a new uniform and widened its subject selection and sports options for girls.
In its first year as a co-ed school, it took in 85 students – 70 boys and 15 girls – including Megan Hurley.
The following year enrolment surged to 140 students, with an equal split of boys and girls.
“The atmosphere changed overnight,” said Mr Wolfe. “The girls calmed the boys down, and boys calmed the girls down.”
At a time when gender-based violence is under growing scrutiny, it has sparked a revival of the debate about whether single-sex schools are healthy environments.
Latest international data indicates that Ireland has the second-highest concentration of single-sex education in Europe, second only to Malta.
The Labour Party is due to publish a private members' Bill this week seeking an end to single-sex education at primary within 10 years and secondary within 15 years.
As far as Mr Wolfe is concerned, there has been a dramatic softening of culture and growing sophistication at the school.
“The dynamics of the school changed. The tougher guy isn’t the most popular anymore. The softer boy – who might be into drama rather than sport – is suddenly very popular and had a wider group of friends.”
There were also unexpected changes in subject choice, such as the introduction of home economics. It is now one of the most popular classes among boys and girls in the schools.
For the Leaving Cert Applied, the school swapped ICT for hotel catering and tourism.
“So, now you have lads, who might not have been the strongest mainstream learners taking it all so seriously. It’s brilliant. I saw one of them arriving into school, chiding another: ‘Hey, be careful of my eggs.’ We’ve a fabulous home economics teacher, which really helps.”
He feels the change has created a more welcoming environment for transgender students and promoted greater levels of empathy and understanding.
“It really is the best thing we’ve ever done – especially when I see boys and girls calling for each other, rather than having gangs of one sex and the other. It’s more natural. They have a better understanding of each other. It’s how college is; it’s how society is.”
However, many single-sex schools are happy with their status and have no wish to change their enrolment policies.
Barbara Ennis, principal of Alexandra College, a fee-charging , all-girls' secondary school in south Co Dublin, said her students benefit from a greater emphasis on female empowerment, achievement and self-esteem.
Proposals to abolish single-sex schools, she said, are the wrong answer to a much broader question.
“My view is this violence against women has little or nothing to do with schools and more to do with what people experience at home and what they see in society. Abolishing single-sex schools is irrelevant. This is about wider society,” she said.
Ms Ennis feels single-sex girls’ schools allow students to have a “safe space” in which to express themselves through drama, speech or music.
“While I’m sure that would work in a co-ed school, I think there is a risk it would get dominated by boys. Here, they feel safe to experiment with different version of themselves. It’s a safe, empowering environment.
“The idea that we would have a better school community if we were co-ed is not something I subscribe to. If we start abolishing things, we become very dictatorial; we see freedom being taken away,” she added.
When asked for its views on the issue, the Department of Education said questions such as whether schools are single sex or co-educational rested with school patron bodies, subject to the agreement of the department.
It said new schools are generally co-educational in nature and provide greater flexibility than single-sex schools in meeting demographic requirements in an area.
However, it said single-sex provision may be made if there is an identified imbalance between the capacities of single-sex schools in the area.
“Similarly, where the extension of capacity at existing schools is identified as the preferred solution, the expansion of co-educational schools is typically preferred,” a department spokeswoman added.
One of the arguments in favour of retaining single-sex schools has been their superior academic performance.
However, Prof Emer Smyth of the Economic and Social Research Institute said the most recent reviews of Irish research have shown "very little consensus" on whether single-sex education leads to better outcomes for girls or boys.
“There are a lot of myths circulating about the relative merits of single-sex and co-education,” said Prof Smyth.
“Single-sex schools, on average, are more middle-class in intake and tend to draw students of higher initial ability. When we adjusted for social class and prior ability we found no significant different in the academic outcomes of students from single-sex and co-ed schools, in either the Junior or Leaving Cert.
“There was far greater variation between schools of different levels of advantage – that’s the real issue.”