Critics of faith schools have long complained of skewed admissions policies that favour middle-class pupils, so it came as a major surprise last year when the Church of England appeared to agree that they had a point.
The Right Reverend John Pritchard, Bishop of Oxford, who chairs the CofE's national board of education, provoked a storm of controversy by saying that schools should stop collecting "nice Christians into safe places" and instead cut the number of places reserved for Anglicans.
That debate is now set to be reignited at the General Synod - the legislative body of the CofE - which, for the first time, will host a campaign organisation opposed to school places being determined by faith.
The invitation to the Accord group has been made by Synod member the Reverend Hugh Lee, who has warned that faith schools risk creating sectarian "ghettos". Speaking to TES ahead of next week's debate, Reverend Lee said that faith school advocates should learn lessons from segregation in Northern Ireland.
"It seems to me very important that faith schools should be open to different faiths, rather than closed and creating ghettos," he said. "School admissions can certainly be a problem. I would encourage people to look at Northern Ireland. That situation is now improved, but it is an example for others to be aware of. It is important that whoever is running a faith school is aware of the issue of segregation.
"Faith schools need to think very carefully about how open their admissions policies are and whether they are contributing to sectarianism and strife or integration and harmony."
When the Bishop of Oxford made his intervention in an interview with TES last year, he suggested that CofE schools limit the proportion of places reserved for Anglicans to just 10 per cent.
The Accord coalition - whose members include religious groups and teaching unions - does not object to the existence of faith schools, but is against them being allowed to select any pupils or staff based on religious observance.
Rabbi Dr Jonathan Romain, chair of Accord and minister of Maidenhead Synagogue, said that he had met with the Bishop of Oxford to discuss the issue. The meeting is likely to foment distrust among some more traditional members of the clergy, who are opposed to the Bishop's desire for reform.
"It was very refreshing that he dealt with a general perception that church schools were closing ranks," said Dr Romain. "He seemed to be going against the grain of what many from within the Church had said before."
Dr Romain said there was also "no doubt" that some members of the clergy would regard Accord's presence at the Synod as controversial, but he added that his organisation was very keen to work more closely with the Church.
"One can value faith, but also be worried by the thought of schools becoming religious ghettos," said Dr Romain. "It is unhealthy both for the children attending such schools and for the children at community schools increasingly denuded of Anglican, Jewish or Muslim pupils. If we want children to love their neighbour as themselves, they have to actually know them."
Reverend Lee, who is also from the Oxford diocese, said that the Church had to move to a greater consensus on admissions.
Jonathan Bartley, co-director of the theological thinktank Ekklesia, who will also speak at next week's debate, said he was concerned that CofE schools did not accept more children with special educational needs or those who are eligible for free school meals.
He added that the number of voices calling for change on reserved religious places was growing.
"It is not a situation that is going to change overnight," said Mr Bartley. "There are strong opinions on both sides. But since the Bishop broke ranks last year, it has become clear that there are growing numbers of senior people in the Church who support him."
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Around half of the Church of England's 4,800 schools are voluntary-aided, which means that they control their own admissions policies and can reserve places for Anglicans and other Christians.
After stating that he was keen for schools to limit reserved places to 10 per cent, the Bishop of Oxford issued revised admissions guidance to dioceses.
However, the guidance did not include a target figure. The Bishop can only advise dioceses and schools and does not have the power to make them comply with directives.