Sydney Anglican archbishop Glenn Davies has apologised "to the community" but refused to back down from a letter to the Prime Minister calling for exemptions to enable religious schools to discriminate against LGBTQI students.

Key points: Sydney Anglican Archbishop says expelling gay students or gay teachers not part of church's ethos

Sydney Anglican Archbishop says expelling gay students or gay teachers not part of church's ethos He says there's "widespread misunderstanding" of church's position

He says there's "widespread misunderstanding" of church's position Petition, signed by at least one former student from 33 of the 34 schools involved, will be sent to PM

The letter, signed by 34 Anglican schools and sent to the Prime Minister last week, caused a furore, with thousands of former students from the schools involved slamming the letter's content.

Speaking to the ABC, the Archbishop said the church simply promoted religious freedom.

"We don't expel gay students," the Archbishop said.

"We don't dismiss gay teachers, that's not our ethos in Anglican schools.

"Rather, what we want to do is promote religious freedom."

The Archbishop said he wanted to express his personal sorrow and apologise to the community.

"But I don't want to apologise for requiring or requesting religious freedom," he said.

The Archbishop said there had been a "widespread misunderstanding" fuelled by, "parts of the media with regard to what our position is".

But he acknowledged there had been "a risk" of alienating people.

"There has certainly been a backlash, particularly among some of the north shore schools.

"I acknowledge that and hence my apology," he said.

"But it's also true to say a lot of the schools have not had that backlash, a lot of the schools have actually had letters of support."

Pressure to retract letter mounts

The response from the former students of the Anglican schools that signed the letter continues to grow.

Hundreds of people are expected to march down the Pacific Highway from the Abbotsleigh and Barker College schools on Saturday in protest.

Max Loomes, who graduated in 2013 from St Luke's Grammar School in Dee Why, has pulled together a petition with 2,800 signatures, calling for educators to withdraw support for the exemptions.

Max Loomes is a former student from St Luke's. He started a petition, which now has 2,800 signatures, to call for headmasters and headmistresses to retract their support for the Diocese's letter. ( ABC News: Kevin Nguyen )

The petition, which launched last week, will be sent to each of the headmasters and headmistresses, Prime Minister Scott Morrison and NSW Premier Gladys Berejiklian.

It contains at least one former student from 33 of the 34 schools who signed onto the original Diocese of Sydney letter.

"The response was huge, it was a giant explosion of signatures and anger from all these different schools," he said.

"The first step is all the schools should retract their signatures from the open letter.

"It's important for the schools to show support to all their gay and lesbian staff and all their students."

He said even if a private school wanted the right to discriminate, it should not enjoy taxpayer funding.

Yesterday, the ABC reported 580 former students from St Catherine's had sent the current headmistress a letter, imploring her to retract her name from the original letter.

Another Anglican school leader apologises

One of the signatories of the Diocese of Sydney's letter was Tim Wright, the headmaster of Shore School in North Sydney.

He is the third head of an Anglican school to apologise for the letter and call for the removal of the exemptions.

"We recognise the exemptions have got to go," Dr Wright said.

"It's silly for us to have even thought that it made sense for us to retain those and not use them," Dr Wright said.

"You always have to take responsibility, it's the whole theory of leadership I live by — I am responsible and I will be accountable."

Dr Wright said the position of the Anglican Church is that discrimination should not be legislated and those exemptions were a "loophole" to retain freedom of religion.

He lamented the direction the debate had gone and regretted the sense of despair many students had felt.

"It raised painful memories of rejecting and suffering for many people, including [former students] who felt rejected by peers or not allowed to be who they were."