The site, which houses 1,700 pupils and 215 teachers from St David's High, Dalkeith High and Saltersgate special school, has rarely been out of the headlines since it opened in August over allegations of religious tensions and fears about pupil safety.
But an unscripted "God bless you" from Jack McConnell, the First Minister, who was officially opening the campus, was as religious as it got on Monday.
Cardinal Keith O'Brien promptly issued a statement saying he was "saddened" by the absence of any prayer or blessing from the official proceedings. He was, literally, kept in his place on the platform along with the Very Rev John Cairns, a former moderator of the General Assembly of the Church of Scotland.
Presumably if the Cardinal had spoken, the organisers would have felt obliged to provide balance by offering the same facility to the ex-moderator.
This contrasted with the political leadership of Midlothian Council, no fewer than three of whose leading councillors strode to the microphone to extol the ground-breaking venture, which shares playgrounds, dining areas and offices but not teaching. The politicians clearly intended the ceremony to be a secular affair.
The opening remarks of the day were none the less carefully crafted, so much so that they could almost have been choreographed. Mr McConnell said:
"This campus is not about eroding differences - it is about celebrating difference."
The First Minister added later: "Scotland's Catholic schools have an excellent record of educational achievement and they should continue to receive government support as long as parents want that choice. Shared campuses are one way to secure the future of both traditions, and they should be seen in that context."
Despite his reservations over the absence of prayer, Cardinal O'Brien's statement responded by welcoming Mr McConnell's call to "celebrate diversity". He was careful to say, however, that shared campuses are only one approach in this endeavour while "stand-alone schools" are another.
Mr McConnell will have to confront some of the sensitivities involved on possibly a greater scale in his own constituency backyard as North Lanarkshire advances its ambitious plans to combine Catholic and non-denominational primaries on seven shared primary school campuses.
In a clear exhortation to staff which he may well find himself repeating in the future, the First Minister declared: "Whether schools are two miles apart or two buildings side by side, all of the adults involved have an absolute duty to encourage tolerance, respect and understanding."
The proceedings culminated in a symbolic show of harmony as a samba band of players from all three schools gave a rousing performance and a "diptych" of artwork produced by two pupils from each school was presented to Mr McConnell.