Mr McGrath concedes that many of the characteristics of Catholic schools are shared with other schools. I would say that the convergence, at least in the secondary sector, is of the order of 95 per cent. That was not always the case, but many Catholic schools have toned down their Catholicism over the years.
Why have they done this? Mainly because the change corresponds with the feelings of Catholic parents, who are much less sure of their faith commitment than earlier generations. The ever pragmatic Cardinal Keith O'Brien has keyed into this change, saying that the future, if any, of the Catholic sector rests with the parents, not with the hierarchy.
A subsidiary reason is that Catholic schools have gone out of their way to make themselves attractive to a certain type of non-Catholic parent, the kind of person who seeks an education that emphasises academic achievement, moral values and good discipline. This is a far cry from the position, only a few years ago, where Catholic heads, especially in Glasgow's leafy suburb areas, were calling for entry to their schools to be restricted to baptised Catholics.
While the new attitude may seem to be tolerant and outgoing, it contains the seeds of the eventual downfall of the sector. If part of the parental and pupil body has chosen a school for non-religious reasons, then there is pressure from that body to have further toning down of the specifically religious features of the curriculum and ethos, especially where many of the nominally Catholic parents are complicit in the process.
There is further confirmation of this erosion of Catholic identity in last week's news that a new joint secondary campus in Bearsden and Milngavie will involve joint teaching of all subjects except religious education, biology and personal and social education. Again, this is defended, by Mr McGrath himself, on pragmatic grounds.
For a religious community, pragmatism is a dangerous master. It provides cover for the hidden religious doubts and the social ambitions, which are healthy in themselves but also favourable to integration, of many Catholic parents.
In my time, Scotland's central belt Catholics have gone from being an embattled minority to being a self-confident and relatively socially integrated element of the community, albeit laying themselves open to continued discrimination because of the existence of separate schools.
If only they could take the final step: come into line with Catholics in the north and south of Scotland and in the islands and accept that religious identity may be preserved without a socially divisive school system which is, in any case, in a state of terminal decline.
Fred Forrester North Larches, Dunfermline