Cardinal Thomas Winning, leader of Scotland's Roman Catholics, told The TES Scotland: "The most basic issue at stake here is that Catholic schools exist for Catholic children. That is why they were set up, that is why they continue in existence.
"Just two weeks ago, the Pope said to me and other bishops of Scotland: 'I am aware that you have vigorously reaffirmed the Church's right to establish, conduct and govern schools freely and in accordance with the right of Catholic parents to have a means of ensuring their children's education in the faith.
"'Whenever these rights are threatened, a decisive response is called for.' "Choice in itself is a good thing, and the Church upholds the parent's right to choose - the choice of a Catholic school is after all an example of a parent using his or her right to choose.
"However, I would be concerned that the right could be exercised in such a fashion that popular Catholic schools received so many placing requests from non-Catholics that Catholic pupils could not get into Catholic schools in their area because there were too many placing requests from others.
"So I would welcome a change in the workings of the system which would formally give priority to Catholic children when it comes to placing requests for a Catholic school."