Ethos is too small a word
For at least half a century, the staff of Catholic schools have included non-Catholic teachers. At first this was mainly an east of Scotland phenomenon (Edinburgh, Fife, etc), but it has spread steadily into the west central heartlands. The sector simply could not continue without the services of such staff.
Catholic representatives on education committees have increasingly adopted the stance that it was not for them to examine the religious belief and character of non-Catholic members of staff. This is partly a matter of principle, commendable in its own way, and partly pragmatic. You quote Bishop Devine as saying that the new "charter" provides the church with "a way of giving approval, but not in terms of religious belief and character". This is inconsistent with the Education (Scotland) Acts, which specifically provide that religious belief and character is the one area over which the denomination in whose interest the school is conducted has a veto on the appointment of teachers. This test applies to all teacher appointments to the staff of a denominational school. Where an appointment is made, the test is deemed to have been applied. A move from a test of religious belief and character to a more generalised test of the applicant's attitude to the aims, values and ethos of the school would require legislation, which, in the present climate of opinion, would be unlikely to be enacted.
I can see where the Catholic authorities are heading. They see ethos as the final bastion of the identity of the sector, the feature that will mark a school as Catholic even where a majority of the teaching staff and a large minority of the pupils are not Catholics. However, I doubt whether ethos, which is a rather undefinable concept, can bear the burden being placed upon it. Certainly, the current legal foundations of the Catholic sector, while making reference to religious instruction and to the religious belief and character of the teachers, do not use the word "ethos" or, indeed, the words "aims, mission and values".
This attempt to modernise the arrangements for the Catholic sector is more likely to result in exposing the contradictions inherent in maintaining a faith school sector within a mainstream education authority system.
Modernisation of an institution may prolong its life or may lead to its downfall. In this instance, I suspect that the latter will be the case.
58 North Larches Dunfermline