To the affluent commuters passing by, Vishnitz Girls School looks like any other well-maintained North London townhouse.

Were it not for a glimpse of white-shirted backs hunched over desks in the front room, you would not even suspect it was a school.

Unlike most primary schools, there's no brightly-coloured sign advertising its presence. Indeed, a black-clad security guard in his sentry hut seems to be there mainly to keep unwanted visitors away.

Students at a Jewish school in North London celebrate Hanukkah. Haredi Jewish tradition insists on separation of genders during schooling

With good reason. As one of a handful of Orthodox Jewish schools in Britain, it's a prime target for terror attacks. Just across the Channel in France, similar schools have suffered unthinkable atrocities.

Yet the threat facing Vishnitz Girls School today does not come from Islamic extremists. Instead it is under attack from a force far closer to home; a force which wants to see it, and other faith schools like it, conform to a different ideology or be summarily closed down.

The unlikely battleground for this is LGBT (Lesbian, Gay, Bisexual and Transgender) rights. Last month, Vishnitz Girls School — where the teaching of Jewish and religious studies was singled out for praise by inspectors in its first Ofsted report of July 2013 — was presented with an ultimatum: teach your children about homosexuality and gender reassignment, or we will close you down.

In the space of four years, Ofsted inspectors have now graded it as a failing school, based on this sole issue.

To those who run Ofsted it is a noble cause. But to the Haredi Jewish families who send their daughters — aged three to ten — to the school, it represents an impossible dilemma.

Members of this conservative community — 30,000 of whom are centred on Stamford Hill, North London — are instantly recognisable by their black hats, ringlets and frock coats.

In their tradition, which, like Islam, involves segregation of the genders, the issue of sex education falls to parents rather than schools. The notion of teaching a seven-year-old Haredi girl about gender reassignment is anathema. Yet as far as Ofsted is concerned, Haredi schools face a simple choice: abandon a key religious principle or be closed down.

This is no isolated curiosity, affecting only the 45,000 or so British Haredi Jews. To people of faith, it is a familiar tale of the Left launching a sustained attack on religion.

Now those involved in Christian schools are linking arms with Orthodox Jews to challenge what they see as the Department for Education (DfE) pushing a secularist agenda.

As Gill Robins, of Christians In Education, puts it, the DfE has launched 'an all-out assault on faith values, sanctity of family and parental rights'.

Orthodox Jews outside a synagogue in north London (file picture). In their tradition the issue of sex education falls to parents rather than schools

Ofsted stands accused of 'targeted attacks' on faith schools, turning up without warning for inspections aimed at forcing them into closure.

In 2014, when Nicky Morgan succeeded Michael Gove as Secretary of State for Education, she made the significant step of hiring Luke Tryl, who campaigned against homophobic bullying as head of education at the gay rights group Stonewall, as a special adviser.

His close ties to the Cabinet minister gave him huge influence and his appointment in 2014 coincided with a marked change in the approach to teaching LGBT issues in Britain's schools.

The following year the charity Educate & Celebrate was handed £214,000 from a Government budget of £2 million to tackle homophobic, biphobic and transphobic (HBT) bullying in schools. Part of this money was used to circulate books which taught children as young as seven to stop saying 'girl' and 'boy' so they did not offend transgender pupils.

Mr Tryl, a former president of the Oxford Union, is a seasoned lobbyist who says homophobic bullying is 'endemic' in schools.

Yet there is a growing sense among teachers who do not subscribe to this mantra that this has hijacked the wider issue of bullying.

'We have gone from anti-bullying campaigns to the specific issue of homophobic bullying, which is by its very nature more of a niche concern,' says Gill Robins.

'But anyone who raises an eyebrow is attacked as a bigot. We have this liberal elite who feel everything in education has to be rainbow-coloured. It is getting out of hand.'

When Theresa May sacked Nicky Morgan last summer, Luke Tryl was appointed Director of Corporate Strategy at Ofsted, and the campaign appeared to step up a gear.

Take Ofsted's inspection of Beis Yaakov High School, a Jewish academy school in Salford, where the all-female pupils have lived sheltered lives with gender segregation and for whom social media and smartphones are unknown entities.

Not a life to everyone's tastes, but Britain has a proud tradition of tolerance, allowing others to pursue their religion without interference.

Clearly nobody had told the Ofsted inspectors. During the inspection, the girls were asked questions such as: 'Do you have a boyfriend?'; 'What do you know about men being married to each other?'; and 'What do you think about Facebook?'

Nicky Morgan (pictured) hired Luke Tryl, who campaigned against homophobic bullying as head of education at the gay rights group Stonewall, as a special adviser

While a number of Islamic faith schools have been closed down following similar inspections, there is a crucial difference. In the case of Islamic schools, there have been genuine fears about extremism, with teachers actively instructing pupils that it is acceptable for a man to beat his wife and that gay people should be put to death. Some were even found to be providing access to banned extremist textbooks.

None of this is true of the Jewish schools, especially Beis Yaakov.

All indicators showed that the Greater Manchester school was outstanding, with a varied curriculum, supportive staff, happy parents, 'positive and enthusiastic' students who are 'impeccably polite', 'enjoy taking responsibility' and behave so well that 'exclusions are non-existent'.

Yet because of the pupils' bemused responses to those insensitive, inappropriate questions, the school was put into special measures. This meant it was graded as failing and was subject to inspections every three months until changes were made.

Beis Yaakov returned to a grading of 'good' within a year. This involved the school amending its PSHE (Personal, Social, Health and Economic education) classes to include discussions of homosexuality and transgender issues. The distress suffered by students as a result of the continued inspections was such that the school made a formal complaint.

There was a similar disconnect between the quality of education and Ofsted's mark at Vishnitz Girls School.

The school's first Ofsted report in July 2013 found the school 'good' in all areas, saying: 'The girls make good progress in their Kodesh (Jewish/religious studies).' It continued: 'Teachers know the girls well so that the needs of the girls are met well and they are eager to learn.'

Three years later, in February 2016, the school was subjected to its first unannounced inspection. Ofsted found that supervision was good, but it did not have up-to-date policies on safeguarding and the buildings required maintenance work.

While the report contained no criticism of the school's teaching standards, a line at the end of the report states: 'The aims and ethos of the school are governed by the codes of the Torah and are based on the three tenets of Judaism: Torah, Prayer and acts of loving kindness.'

By the time of the second inspection in October 2016, Ofsted noted that while progress was being made in the areas highlighted by the February report, 'the school's policy to exclude from the curriculum reference to certain of the protected characteristics in the Equality Act 2010' meant it had again failed.

By the third visit, in May, every issue in the first failed report — down to peeling paint on a wall — had been resolved. Pupils were also deemed to be 'well-motivated, have positive attitudes to learning and are confident in thinking for themselves'.

However, it also found that: 'Pupils are not taught explicitly about issues such as sexual orientation. This restricts spiritual, moral, social and cultural development and does not take account of differing lifestyles.

'As a result, pupils are not able to gain a full understanding of fundamental British values. [Teachers] do not teach pupils about all the protected characteristics, particularly those relating to gender re-assignment and sexual orientation. This means that pupils have a limited understanding of the different lifestyles and partnerships that individuals may choose in present-day society.'

Through Ofsted's rainbow-coloured lens, schools either pass or fail, and in hindsight this tiny Jewish private school, with annual fees of £5,500 and just 212 pupils, never stood a chance.

The injustice of it all has provoked fury in the Haredi community. Rabbi Abraham Pinter is scathing in his criticism of Ofsted. The rabbi, who is principal of Yesodey Hatorah Senior Girls' School in Stamford Hill, made a Freedom of Information request to ascertain how many schools had been subjected to unannounced inspections in the latter half of 2014, when they were introduced.

Ofsted papers revealed that 13 schools were subjected to full unannounced inspections (which are only meant to be carried out in cases of 'serious concern'), of which three were Orthodox Jewish.

Two were Roman Catholic, one Church of England and the rest standard secular secondary schools. In terms of the proportion of schools targeted, the Jewish examples were vastly more likely to be picked on, despite being routinely among the best performers.

'There are only ten Orthodox Jewish schools in Britain, so effectively one in three were singled out for the heavy treatment,' says Rabbi Pinter. 'This is social engineering at work and nothing to do with safeguarding our children.'

Referring to the Vishnitz case, he condemns the 'obsession' with fighting 'non-existent issues for our community'.

'I suggest Ofsted go down to the local police station and ask them about the history of homophobic abuse around here,' he says. 'There is none whatsoever. We are decent, tolerant people and we do not bully anybody. So why should we be forced to teach girls about issues which have nothing to do with their lives? Our community promotes tolerance of all . . . But tolerance works both ways; Ofsted shows none to people of faith.'

Several Christian faith schools were among the 40 subjected to unannounced Ofsted inspections in late 2014 and on numerous occasions since then.

All were found to be failing 'British values' because although their pupils are respectful and tolerant of difference, the schools all teach that marriage is defined in the Bible as being between a man and a woman. All, because of this point, were downgraded from good to inadequate.

It is worth pausing to consider the terminology. 'British values', according to Ofsted, appear to be defined as placing the rights of people with 'protected characteristics' (in this case specifically the LGBT community) above the right to religious freedom.

When Parliament's Secondary Legislation Scrutiny Committee considered this term, it described the DfE as merging 'statutory provision with political declaration'.

In other words, the DfE and Ofsted have been politicising the curriculum, breaching both human rights and education law.

As Gill Robins puts it: 'Under the guise of a Trojan Horse, the DfE is seizing an opportunity to bring all schools firmly into line in promoting its views on creation, sexuality and relationships.'

So where do the schools go from here? The problem with appealing an Ofsted decision is that complaints are dealt with by the quango itself. Worse still for beleaguered faith schools, all unannounced inspections are carried out by Her Majesty's Inspectorate, Ofsted's elite unit. So for the faith schools to win, these HMIs would be required to overturn their own decisions.

A spokesman for Ofsted says the rules were set by the DfE, adding: 'The standards require all independent schools to actively promote fundamental British values and equalities, including respect for those with different faiths and beliefs.

'These standards are enshrined in law. Schools cannot choose which parts of the legislation they comply with.'

The DfE issued a statement reiterating its stance that 'all schools must prepare pupils for the opportunities and responsibilities of life in British society': 'Any school that fails to meet these standards will be subject to regulatory action to ensure every child is getting the excellent education they deserve.'

And so the war goes on. Shimon Cohen, speaking on behalf of Vishnitz Girls School, tells me: 'We are deeply disappointed that Ofsted feels our school has not met the Independent School Standards, particularly when its decision is focused on one complicated issue that is contrary to our beliefs.

'We would like to thank the many people who have shown their support and we are heartened that there are still people who hold to true British values of tolerance to all religions and beliefs.'

A strongly worded, yet admirably restrained response, it barely hints at the fury felt by parents of children at the school.

But if Ofsted's ideologues think this community will be cowed into submission, they can think again.

'This is a line in the sand and we will not cross it,' one parent told me this week. 'The mistake Ofsted has made is in thinking we have a choice in the matter, but religion is our lives, and we will not budge.'