Catholic schools should retain their own identity under any shared campus agreement with a non-denominational school - and that includes separate pupil toilets and staffrooms.
The Catholic Education Commission pre-empted the latest furore earlier this year by drafting guidelines on shared campuses as local authorities stepped up their school rebuilding plans under the public private partnership initiative.
As ever, the commission attempts to balance the need for new buildings with its defence of Catholic education and opposes "any scheme which could be construed as social engineering".
Its working group states: "We are aware that there are those both within and outwith the Catholic community who regard 'shared' campuses as a means of phasing out Catholic schools. Understandably, we totally oppose such strategies."
The group demands the continuation of free-standing Catholic schools, although it accepts that "in exceptional circumstances" shared campuses may bring improved facilities. "We would, however, require to be assured that such arrangements would preserve the identity, distinctiveness and ethos of the Catholic school," it continues.
So far, only one secondary shared campus, involving St David's and Dalkeith high schools, is under way in Midlothian.
John Oates, CEC field officer, re-emphasised this week that "this is not a merger" but a sharing of facilities.
"If you read inspectorate reports, you find that ethos contributes greatly to the quality of education and there are sound educational reasons why we prefer free-standing schools. It's far easier to develop your own ethos in your own environment," Mr Oates explained.