As Labour edges closer to power, any hindrance to that goal is being ruthlessly removed. The £28 billion pledge in green spending has been dropped; plans to elect the House of Lords delayed. Bankers’ bonuses will remain uncapped. City financiers are subjected to prawn cocktail offensives at £1,000-a-head soirées to hear Rachel Reeves preach fiscal probity. ‘My instinct is to have lower taxes,’ the shadow chancellor insists.

Yet it’s an instinct that seems absent when it comes to easy targets such as the 2,500 independent schools in England and Wales on which Reeves wants to levy VAT and business rates. Both publicly and privately, Labour insists this pledge will remain. Insiders view it as that rarest of policies: a popular revenue-raiser. Labour cites figures by the Institute for Fiscal Studies (IFS) that suggest VAT on fees could raise £1.6 billion for the state sector. Polls show a majority of every demographic group support VAT on private schools – except those who went to one or have a child at one.

Analysis by the IFS admits that up to 40,000 children could be pushed into the state system

Critics of the policy are derided as mere purveyors of privilege. ‘It’s their equivalent of the £350 million a week for the NHS,’ warns Iain Mansfield, of Policy Exchange. ‘A clearly popular policy that their opponents can’t stop themselves talking about.’ Yet that hasn’t deterred a rearguard effort to try to save the schools affected. Leading the charge to highlight the dangers of Labour’s policy is the Independent Schools Council (ISC), based in an 18th-century townhouse in Westminster. Most of the ISC’s 1,400 members are, in the words of its chief executive Julie Robinson, ‘little schools with a few hundred pupils’. While the likes of Eton, Winchester and Harrow have pockets deep enough to afford the changes, others, she says, will not be able to do so. ‘We think there will be an immediate effect and then it will take four years for it to be felt. By then, the damage will be done and those schools won’t be coming back.’

Already, Robinson hears anecdotal accounts of a drop in applications to such schools ahead of September. An overall reduction in pupils of 25 per cent is ‘reasonably likely’, according to Baines Cutler research for the ISC. This translates to about 135,000 children.

The case for parents is also being made by the newly launched Education Not Taxation group run by Tony Perry, whose son attends LVS Ascot in Berkshire. The group launched at the end of January and is spearheading a petition that has attracted more than 100,000 signatures. Perry is keen to meet Starmer and Reeves and explain his son’s needs. ‘I want to buy them breakfast,’ he says, ‘so they can look parents like me in the eye and hear our concerns as they have done with others.’

Some people highlight, too, the good work done by the independents, with 85 per cent of ISC members partnered to state schools. Brighton College offers 24 scholarships to Ukrainian refugees and supports the London Academy of Excellence in Newham, where last month 35 pupils got Oxbridge offers. ‘Labour needs to ask itself: is education a public good or not?’ says head-master Richard Cairns. ‘It seems puzzling and counterintuitive that the Labour party is putting forward a tax on education.’ Five of his pupils received places in January to study medicine at Oxford, with their future careers likely to be spent working in the NHS. ‘That would be regarded as a public good in virtually every other advanced economy.’ Indeed, a KC whose opinion the ISC sought suggests that Labour’s plans would not be lawful if the UK were still a member of the EU and had to follow its directive on VAT.

Nonetheless, it is the prospect of school closures that remains the major talking point in the ISC’s efforts to ward off VAT on fees. ‘We are encouraging schools to make contact with local politicians to put across their case as local constituents, local employers,’ says Robinson. Efforts to woo the shadow education secretary, Bridget Phillipson, were hindered after emails were made public in which ISC staff referred to her as ‘very chippy’. Subsequently, at the party conference last October, not a single Labour MP attended the ISC’s drinks reception. Instead, private schools have lobbied Labour councillors and MPs, who in turn have made representations to Phillipson. Useful allies are found in the teaching unions, who warn of the impact on jobs, pensions and pupils. ‘We remain concerned that scrapping tax exemptions for independent schools will result in a significant number of pupils being displaced into state schools,’ says Geoff Barton, of the Association of School and College Leaders.

Opponents echo this by asking what will happen if parents move their children from private schools into the overcrowded state sector. A population bulge is in the process of moving from primary into secondary schools, putting extra pressures on places. A third of children missed out on their first-choice school in London and other parts of England last year. The £1.6 billion figure touted by Labour assumes that most parents can ‘soak up’ the cost of VAT on top of fees. Yet that analysis by the IFS admits that up to 40,000 children could be pushed into the state system.

The EDSK thinktank, meanwhile, suggests that even under a ‘best case’ scenario (based on the Labour party’s projection that 5 per cent of pupils would be forced to leave), the addition of VAT to private school fees would raise only around £1 billion a year – £700 million less than is currently claimed. Under a ‘worst case’ scenario (in which 25 per cent of pupils leave), adding VAT to school fees would essentially raise zero additional revenue. This is why some Conservative MPs view the measure as ‘Keir Starmer’s fox-hunting pledge’: a policy motivated more by class resentment than cost-benefit analysis.

While Rishi Sunak isn’t going to mention school fees much in the general election campaign, other Tories are more willing. A Westminster Hall debate on the subject last month attracted contributions from a dozen Tory MPs but not a single Labour backbencher. It was left to Helen Hayes, the shadow minister for children, to make the case for the opposition’s flagship policy on her own.

Some MPs have highlighted specific local cases in the House. Cathedral schools, for instance, were raised by Lichfield’s Michael Fabricant, who fears that the ancient choral tradition taught in such establishments could be lost. Another MP suggests the fate of independent schools will be an election issue in ‘scores’ of seats and the policy features ‘heavily in parents’ WhatsApp groups’. These seats include some of the capital’s key battlegrounds such as Barnet, Hammersmith and Westminster, where the infamous catchment area issues – ‘the real angst of London’s middle classes’ – would be exacerbated by any school closures. In some boroughs, such as Richmond and Camden, more than three in ten are independent.

Westminster thinktanks are deploying their intellectual firepower too. The Centre for Social Justice has been researching ongoing partnerships between state and private schools, while the Adam Smith Institute is this month releasing a critique of the costs of Labour’s changes.

The real challenge to Labour’s pledge, though, could come after the election. With more than 600,000 pupils potentially affected, a consultation would be likely to prompt vocal calls for special opt-outs and exemptions. The Liberal Democrats are notably against Starmer’s policy, with a dozen schools likely to be affected in Ed Davey’s own patch of Kingston-upon-Thames.

Once Labour are in government, its figures – which are premised on the belief that independent schools will be able to soak up higher taxes – could also come under greater scrutiny. As Jim Knight, a former schools minister under Tony Blair, notes: ‘The Treasury is bound to be worried about any potential increase in cost associated with the displacement of pupils out of private schools into state-funded ones.’ To date, however, such arguments have found little favour with a party whose shadow cabinet is almost 90 per cent state-educated. The core of Labour’s argument is that private schools are now beyond the reach of the middle classes.

‘I believe that the instincts and educational values Sir Keir Starmer learned here at Reigate Grammar School will stand him in good stead,’ wrote the current headmaster of the Labour leader’s alma mater earlier this year. ‘Let’s create cohesion not conflict. Let’s have a conversation, not an argument.’ So far, it is not a conversation that Labour seem much interested in having.