Teaching Matters:Second-level education in Ireland might have been described by one of Sean O'Casey's characters as a "parrotox", writes Breda O'Brien.

In other countries, there is a sharp divide between state and denominational schooling, with the latter usually privately funded. In Ireland, it is increasingly difficult to see where the divide between church and State lies.

In our denominational voluntary secondary schools, the State is the paymaster, albeit with substantial "voluntary" contributions directly from parents. Yet our allegedly State-run community and comprehensive sector has paid chaplains as a right, which the voluntary secondary sector does not. We even have trouble drawing a line between public and private, because in our private schools, the teachers are mostly paid by the State.

Catholicism has had a particularly strong role in second-level education. Whatever Catholic means. It is becoming harder and harder to define. Once upon a time, you knew a Catholic school by the statues on the corridors and the crucifixes in the classrooms. It will never be that easy again. While from one angle it is valid to say that Catholicism has had a pervasive influence on second-level education, from another, it would be equally valid to say that the State is incredibly dominant, setting curricula and standards and providing most of the funding.

There is a lot of soul-searching going on in schools once staffed and run by religious orders. Many congregations are accepting that the decline in numbers entering religious life means that a passing on of responsibility to lay people is the only route to take. Some religious congregations have invested heavily in this process, consulting along every step of the way, and ensuring that the people who will run the schools in the future have a real sense of their heritage and identity. Other congregations have only made puny attempts to do so, and still expect that the process will work.

At a conference run by the Irish Catholic Bishops and Cori (the representative body of religious congregations) in February 2005, a Canadian archbishop proposed that as a minimum, all teachers in Catholic schools should be "practising Catholics committed to the Church and living her sacramental life".

All you could say to that would be: "Too late for that, baby". I am not even certain that it is as essential as he believes. There are lots of excellent teachers, utterly dedicated to the students they teach, who would not meet that description of a committed Catholic, yet who would support, in broad terms, what a Catholic school symbolises. Anyway, whenever commitment to the Catholic church is mentioned, it is sexual morality that is the touchstone, something that has always puzzled me greatly. Why is sexual morality the great arbiter? Why not honesty, integrity, commitment to social justice, or even good old-fashioned compassion?

While it is true that not everyone in a staffroom needs to be some kind of Catholic paragon, you do need a critical mass of people who are struggling to live a Christian lifestyle, and, in particular, strong and effective leadership that sets the tone. Ethos is a very slippery concept, easier to experience than to describe or prescribe. Without a key number of people with a clear vision of what a Catholic school is about all you have left is nostalgia.

There is a growing murmur against the notion of denominational schools, and against Catholic schools in particular. No-one wants to be seen to be discriminating against our Church of Ireland or Muslim friends, but it is perfectly respectable to describe Catholic education as narrow or repressive. In fact, the reality is that Catholic schools are much more likely to suffer from the opposite problem, which is to struggle to articulate exactly what makes a school Catholic. At their best, Catholic schools are humane, liberal, welcoming, nurturing places where children are encouraged to develop their potential. Yet such values are far from exclusively Catholic.

The major challenge is not coming from other faiths, but from pupils from once-Catholic families who are no longer in any sense "buying in" to the Catholic ethos. In what sense can a school, even with a core of committed Catholics on the staff, be described as Catholic if there is no support for that concept from parents?

Both church and State recognise that parents are the primary educators of their children, and that schools exist only because the mandate to educate has been given to them by parents. How can a school describe itself as Catholic if the children entering the school in first year do not know a single prayer, have no idea that reincarnation is not a Catholic doctrine, struggle to name the Pope, and have no notion that Jesus is anything other than a historical figure who told people to be nice to each other?

Perhaps we need fewer Catholic schools. Perhaps we need to stop pretending that every school once run directly by a religious order is still a Catholic school. Maybe we need to admit that there were deeply unchristian practices in such schools even when they were run by religious congregations.

Maybe we need to ask parents how much, if anything, they would be willing to sacrifice to keep their children in a Catholic school. The answers might be painful, but at least they would be truthful, and someone rather central to the Catholic enterprise once said that the truth shall set us free.

• Breda O'Brienteaches at Dominican College, Muckross Park, Donnybrook, Dublin