Sharing facilities with non-denominational schools must not be "the thin end of the wedge to integration", Cardinal Keith O'Brien, leader of the Roman Catholic Church in Scotland, re-emphasised last week.
The cardinal emphatically repeated the insistence of the Church on separate Catholic schooling when he addressed Catholic primary heads at their annual conference, against the backdrop of the wrangle over planned shared campuses in North Lanarkshire.
Buildings were fundamental to Catholic education and had been vital to its existence since the 1918 Education Act brought denominational schools within the state sector.
"We have got to safeguard that heritage and the Church has to be on its toes all the time," he warned.
Shared campuses were not new to Scotland and Fox Covert primary in Edinburgh had run as a joint school for 40 years. Pirniehall and St David's primaries in the capital were a more recent illustration of two separate schools on a shared site.
The cardinal said officials and parents from North Lanarkshire had been to the new site in Edinburgh to see a successful campus but the Catholic communities had not been given what they wanted. "They said 'this is what we want' and they were told 'this is what you'll get' but it has not been what they've been offered at all and rightly Bishop Devine and the Church is objecting to this," he said.
The cardinal said the Church may yet go to law over the battle with North Lanarkshire where it believes the authority is eroding the legal entitlement of Catholic parents to have a Catholic education. "This is not what the Catholic community wants. We want a Catholic school and if it's a campus school we are happy to share certain facilities but this is not the thin end of the wedge towards integration. We're not having it," he insisted.
Bishop Joe Devine, head of the Church in the Motherwell diocese, who is leading the campaign against North Lanarkshire's plans for new shared primaries, said the Catholic Education Commission had set out precise guidelines which the local authority was failing to meet. The commission stated that joint campuses should be "the exception rather than the rule" and were only acceptable within small Catholic communities or in villages.
"My dispute with North Lanarkshire is because it has chosen a policy of joint campus schools in the name of community harmonisation for the foreseeable future whenever and wherever that option is open to them and that massively attacks the fundamental principles we had in drawing up the national guidelines," he said.
The row has centred on details such as separate entrances, staffrooms and toilets.
Bishop Devine said the 1918 Education Act required that the authority "must run the school in the interests of the Church". He found it "amazing" that Peter Peacock, the Education Minister, did not refer to this when he ruled out interfering in the dispute after the Church asked him to intervene.
A second key legal aspect involved any changes to a denominational school.
"If that were to result in a significant diminution of the provision, then the authority would not be empowered to make that change," he said.
The bishop explained that the council had twisted the logic by arguing that there was no change to the non-denominational sector. "That's not what the legislation meant at all," he said.
Lawyers for the Church were this week studying Mr Peacock's reply and may yet go to the Court of Session to press its case, although it hopes to resolve the matter locally.
* There are no worries about a dilution of Catholic education when up to half the pupils in some schools are non-Catholics, Cardinal O'Brien said.
Denominational schools should look ahead to a confident future because of their popularity, even amongst non-Catholics. "Catholic teachers are evangelising and something about Christianity is getting through by what you say and do. Just by living in this atmosphere in our Catholic schools, so much is being handed on to those who are not of our faith," he said.
Bishop Joe Devine, of Motherwell, pointed out that Catholic schools today were different to those of 20 years ago, when all entrants to primary would have been baptised. Anywhere between 10 and 25 per cent of current intakes had not been brought up in the Catholic tradition.