“This is the most humiliating moment of my career,” the headmaster of Shore, Dr Tim Wright, told Guardian Australia. “I love the school. I love the boys. I feel I have let them down. I am sorry.”

Wright was one of 34 headmasters and headmistresses of Anglican schools in Sydney who signed, at the direction of the local church, an open letter calling for fresh legal protections for religious freedom. The letter cited – and did not step back from – rights religious schools already have to expel gay students and dismiss gay staff members.

Wright helped draft the letter. He now calls it an inept communication. “I thought we had put aside the issue of discriminating against gay kids and gay teachers.”

But the minute the letter appeared he had parents and old boys on the line asking: “What on earth are you trying to say? What is this all about?”

The Establishment is appalled. Old boys, old girls and parents with kids at a slew of the most prestigious – and expensive – schools in Australia are demanding to know what’s going on. In the face of this uproar, the heads of Barker and Abbotsleigh have both apologised for signing the letter.

Megan Krimmer of Abbotsleigh said on Tuesday: “Reflecting deeply on the feedback and issues raised, the incongruity between saying Abbotsleigh does not discriminate, and supporting highly discriminatory legislation, albeit temporarily, has become clear.”

Wright adds his name to that list. He says he is devastated by the hurt that has been caused by the letter. “It is just awful.”

He spoke to Guardian Australia from the bush, where he has been meeting old boys – particularly gay old boys – to discuss their time at Shore. Wright admits to finding much of this harrowing. Their message to him is one of rejection that goes way back and hasn’t much changed.

“I think the realisation is growing that the relationship between the LGBTI community and the diocese is badly affected by attitudes of rejection,” says Wright. “We’ve not done a good job of communication.”

Wright says: “We have all been reassuring our gay staff.” Earlier this week he held a Q&A for senior boys at the school. Reports from Shore confirm he faced a lively interrogation. Wright also wrote to parents assuring them: “All staff and students are treated equally at Shore.”

But along with the other heads of Anglican schools, he is calling for protections in law that will allow them to appoint only staff willing to support the “ethos” of their schools. That, he says, was the purpose of that hastily written letter.

But what is that ethos?

Attempts by Guardian Australia over the past few days to have the Sydney Anglican church explain this have proved largely fruitless. The diocese – which is among the most hardline in the Anglican world – actually owns Shore and all the schools whose heads signed the open letter.

A church spokesman, Russell Powell, assured Guardian Australia that the uproar over the letter “was never meant to happen” and claims the Anglicans of Sydney no longer want laws to allow their schools to expel gay kids. Haven’t for years. Perhaps haven’t ever.

So why didn’t the letter say so? “The letter was pressing for positive protection for legal freedom.” So what is the church’s understanding of the “ethos” Canberra is supposed to protect? Surely straight not gay?

Powell demurred. Surely homosexuality remains a grave sin in the eyes of the Sydney church? Powell preferred not to speak about theological matters. He sent reading material. It’s vague.

Wright addressed the question with care and determination. “The ethos has to be about respect, love and humility – the fundamental Christian virtues. We have to get away from defining the ethos in terms of sexuality. There is far more to being a human being than sex.”

David Marr went to Shore