David McNab, a maths teacher at the school for 15 years, has taken the local authority to the tribunal, alleging religious discrimination. But Rod O'Donnell, his headteacher, made clear in evidence that the Church's lack of approval was the key factor in deciding not to interview Mr McNab for the post of principal pastoral care teacher.
Glasgow City Council denies religious discrimination, arguing that Church approval was a genuine occupational requirement.
Mr O'Donnell told the tribunal that he would have interviewed Mr McNab for the post if he had fulfilled the criteria. But he did not have the Church's backing.
Mr O'Donnell, headteacher at St Paul's for six years, said that the first point of contact for a child in difficulties would be the pastoral care teacher. The school could not be expected to put a child on hold until an approved Catholic teacher became available, and this person might have no knowledge of the child or family background.
If the appropriate pastoral care teacher was absent or with another pupil, then another should be able to move in as they worked as a team.
Mr O'Donnell said that the school's five pastoral care teachers did not take classes and developed strong links from an early stage. The system was designed to accommodate a situation, for instance, where a pregnant girl wanted to see a woman teacher.
He conceded that from time to time children might be embarrassed or afraid to approach their pastoral care teacher, because they were afraid of a judgmental response. In many cases, a non-Catholic member of staff could then step in. Catholic guidance staff may provide different advice to non-Catholic children.
Mr O'Donnell said that St Paul's was in an area of multiple deprivation.
Many children had chaotic lifestyles and there was a need for increased pastoral care by the school.
The hearing continues next month.