The next day Mr Mullen, a former headteacher of Holyrood Secondary in Glasgow, narrowly won a battle to make pupils applying to oversubscribed Catholic schools prove a religious attachment to the Church. "If we are going to have Catholic schools, surely to God," he says, "it is reasonable to have Catholics going to them. What is the raison d'etre of Catholic schools if it is not to provide a Catholic education for Catholic children who want it?" These were just two in a recent series of arguments over the future of Catholic education in Scotland.
As it faces the new millennium, the Catholic Church is as proud and protective of its distinctive education system as it has ever been. But what does the future hold? Is it a divisive and anachronis tic system or a high-achieving model for other schools? Roman Catholic schools in Scotland have been doing well over the past 10 years, with pupil numbers remaining remarkably steady at 17 per cent of the school population.
Support for the schools stems in part from research in the Eighties by Edinburgh University, which indicated that when comprehensive education was introduced (post-1965), children in Catholic schools began outperforming their opposite numbers from similar socio-economic backgrounds in non-denominati onal schools. They were emerging with an average of one extra Higher or two extra O grades.
This was good news for a sector which until then had not enjoyed high status. Catholic schools first opened in 1817, gaining state funding in 1918. They were opened to cater mainly for the children of unskilled Irish immigrants who flooded into Scotland, particularly during periods of famine.
"Catholic schools grew out of bigotry against poorer people from Ireland. They protect children from divisions in society. They don't further division," says one Catholic headteacher I spoke to, though not all Catholic parents agree. One mother says it was bigotry that led her to choose non-denominational schools for her daughters. "As a child in Glasgow I remember being sworn at, spat upon and having stones chucked at me when I had to walk past a non-denominational primary on my way to school. Our uniforms made us an obvious target."
Yet Catholic schools are experiencing an unprecedented surge in popularity. Many Muslim and Hindu parents now send their children to them - which is one reason whyChris Mason, Glasgow's Liberal Dem-ocrat leader, says there should be no religious barrier to entry.
At Holy Rood School, the RC high in Edinburgh, 30 per cent of pupils are non-Catholic. The headteacher, Patrick Sweeney, says: "When I was a pupil at St Francis's Primary in Glasgow, in the Fifties, all the pupils and teachers were Catholics, and almost everybody went to Mass on Sunday. The Catholic school of the Nineties is quite different.
"The Parents' Charter has had a significant impact. The roll at Holy Rood has risen from 550 in 1993 to 791 in the current year. Last year's intake came from 32 different primary schools and only about 70 per cent of the children would describe themselves as Catholic."
Judging by feedback he gets from parents, he says they choose the school for its values and reputation. "Catholic schools have no monopoly on morality or high standards, but there is a strong system of shared values,which often expresses itself in a fairly definitive position on discipline and good behaviour.
"Parents are reassured by the knowledge that the Catholic school is still prepared to take a stand on what is right and wrong. Members of the ethnic minorities are attracted by the religious and moral education provided, even though it does not coincide with their own traditional beliefs."
It is difficult to pin down what gives Catholic schools the academic advantage. One Fife head told me: "We can get away with certain expectations of behaviour that non-denominationals can't. A head in a non-denominational school cannot rely on parents and most members of staff having a similar vision of what a child's school should and should not be doing."
And Douglas Willms, one of the authors of the Edinburgh research, suggests that Roman Catholic teachers have higher expectations and make greater demands of their pupils. He says that, for whatever reason, the pupils seem to like the environment. Fewer depart for the private sector and fewer teachers depart for pastures new. That stability is in itself of value to a school.
His view is backed up by a parent who is a practising Catholic, with a child in the first year of a Catholic primary, but who goes into many types of schools as part of her job. "Teaching seems to be more of a vocation in Catholic schools, " she says. "I've found more warmth and caring, more of a sense of wanting to hang on in there when a child in difficulty is pushing their tolerance to the limit.
"I feel that spirituality is at their centre. At my daughter's school they place a lot of importance on the Catholic aspect of education. They say a lot of prayers and she seems almost to be learning more hymns than songs. We wanted our children to be in a Catholic environment and have instruction in the sacraments. We're offering them something they can choose to accept or reject in their own time."
She does not believe Catholicism is diluted by the presence of non-Catholic pupils. "A committed head will keep a strongly Catholic ethos.Also, I welcome the chance for my children to have contact with other children and have an overview of other religions."
So what does the future hold? One headteacher summed up his expectations: "With fewer and fewer practising Catholics, we have to adapt to teaching the children who are in front of us. I think in the millennium our schools will become less Catholic and more Christian. I don't think RC schools are about RC education. They are more about a set of values."