Academies sponsored by Sir Peter Vardy, the evangelical Christian who made his fortune selling cars, have won high praise. The schools are popular with parents, lauded by Ofsted and have achieved good examination results, despite being in some of the most deprived communities in northern England.
But, at the same time, they have attracted more than their fair share of critics and accusations that they are pushing an aggressively religious agenda.
The teaching of creationism in science lessons has been a focus of particular criticism and, in 2004, one school was castigated for asking pupils to consider that God stopped Hitler invading Britain. Now further questions about the role of religion at the schools have been raised after it emerged that senior teachers at the academies, and two others backed by Christian charities, face being banned from opting out of religious education and collective worship.
The TES has learned that two academies and a city technology college sponsored by the Emmanuel Schools Foundation - a charity set up by Sir Peter - have successfully applied to become legally recognised independent schools with a "religious character" (see box below).
That means that the schools, Trinity academy, Doncaster, the King's academy, Middlesbrough, and Emmanuel college, Gateshead, can appoint staff according to their religious beliefs, dismiss teachers who fail to follow their Christian ethos and force heads and deputies to take part in religious worship. An academy sponsored by the Oasis Trust, a Christian charity established by the Reverend Steve Chalke, and at least two backed by the United Learning Trust, an Anglican charity, have the same status.
It effectively gives the academies, which are not officially linked to any church, the same power to hire and fire teachers along religious lines that is currently afforded to denominational faith schools. However, the academies insisted this week that they were not trying to become faith schools, because they do not select pupils by religion.
Nigel McQuoid, director of schools at the Emmanuel foundation, said: "The term 'faith school' does not seem to have a universally accepted definition, though it is commonly understood to mean, among other things, that places are reserved for children who follow the school's faith.
"Emmanuel Schools Foundation does not base the consideration of children for admission on their religion and believes children of all faiths and of none should be able to apply to attend our schools. We believe that such a mix is a healthy context in which to help young people express their beliefs where differences are encouraged, protected and fostered within a true sense of community. Similarly, there is no faith test for staff."
The distinct status of the schools places the Christian academies half-way between a faith and strictly non-denominational school.
The powers came in shortly after Labour's 1997 general election victory, when legislation was passed allowing faith schools to employ staff of a particular religious affiliation. These powers were granted to state-maintained faith schools in 1998 and were extended to fee-paying independent schools in 2003, a bandwagon now being leaped on by the Christian academies.
But what do these powers allow schools to do? The academies have the right to choose heads and teachers "whose religious opinions are in accordance with the tenets of the religion" of the school. They also have powers to dismiss those whose conduct is "incompatible with the precepts, or with the upholding of the tenets, of the religion" of the school.
Trinity academy, in its funding agreement - the contract between the sponsors and the Government - says it will use the additional powers to ensure senior staff co-operate with its Christian ethos.
It says: "The principal, vice-principals and the head of philosophy, theology and ethics (PTE)will be excluded from the right to opt out of the teaching of PTE and the attendance at, and leading of, acts of collective worship consistent with the academy's Christian ethos." The Trinity funding agreement adds that all lessons should be "consistent with biblical teaching".
The Emmanuel foundation's website says that the organisation "holds that God made the world and all that is in it, including mankind whom He made in His image. ESF holds also that the Bible is God's Word to the world and that it is true." At Emmanuel academies, "Christian values and teachings underpin the school", though the "rights of all to hold to another or no faith are respected".
The academies' designation as independent schools with a "religious character" does not give them the same rights as the country's 6,885 state-maintained Anglican, Catholic, Baptist, Jewish, Muslim and Sikh faith schools.
Principally, the academies cannot use the powers to select pupils because the legislation only applies to staff appointments. "Even under these laws, schools are not afforded a blanket exclusion from anti-discrimination laws; rather, the religious restrictions are specific to the treatment of teaching staff," said David Smellie, an education lawyer and partner at Farrer Co. "If a school is registered it gives it a greater ability to appoint staff of a similar religious character. It gives a school some protection against religious discrimination law."
Academies, as privately sponsored independent state schools, can already draw up their own rules on the curriculum, staff pay and conditions, admissions, exclusion, RE and collective worship. The protection to employ staff of particular religious leanings simply strengthens the freedom many already exercise over faith.
Mr McQuoid said: "Emmanuel Schools Foundation is a Christian foundation, based upon biblical Christian principles and yet not aligned with any individual denomination. In order to remain true to these principles and to safeguard them for the future, Emmanuel college was granted designation as a school with religious character under statute.
"It is consistent with our ethos that staff, and children, are not compelled to attend acts of collective worship. The leadership of our schools is centred upon a Christian ethic and so it is also consistent that we reserve the right to ask that the principal, vice-principals and head of religious education attend assemblies and other key events."
But secular groups criticised the designation of the powers. Keith Porteous Wood, executive director of the National Secular Society, said: "These schools are effectively getting the benefit of employment policies that are afforded to faith schools without actually declaring 'that is what we are'."