The debate over grammar schools is about to reignite.

Kent County Council has this afternoon voted in favour of a proposal to allow a grammar school in the county to open a new campus.

On the face of it, this is nothing more than a straightforward matter of allowing a popular school to add more capacity so it can accommodate more pupils.

But in fact, this is a highly significant moment, especially for the Conservative Party. If it goes ahead, this would be the first physical expansion of a selective state school for decades. (It’s important to note that grammar schools were already free to add more pupils – they just can’t open new sites.) Under legislation introduced by the Labour government in 1998, no new grammar schools can be opened, but changes in the amended Schools Admissions Code, which came into force on the 1 February, mean that oversubscribed schools are allowed to expand beyond their existing boundaries.

Critics have termed this a way of expanding selection by the backdoor. It’s a potentially landmark change of direction in education policy, but it hasn’t come about because of a major public or parliamentary debate. So far only communities in Kent and Devon have expressed interest in the satellite campuses, but there's no reason why others can't follow suit - Conservative MP Rob Wilson told Total Politics earlier that he is “delighted to see the expansion in Kent” and “sees room all over the country for existing grammars to expand the scope of their activities”.

In some ways, this is an ideal situation for anti-grammar school Conservatives like David Cameron and David Willetts. Grassroots supporters and vocal backbenchers can be appeased with new grammar schools without the need for to engage in an emotionally-charged debate about the merits or otherwise of grammar schools and selective education. That said, if this expansion were to set a precedent that was followed by other selective schools, it will be both embarrassing and politically damaging for the Conservative cabinet ministers who have sustained their opposition to more grammar schools, and they would be forced either to U-turn or to amend the Admissions Code again to remove the oversubscription provision has sparked this debate.

Since 2007, it has been official Conservative Party policy not to favour the creation of more grammar schools. Conservative members of the cabinet might prefer a completely non-selective education system, but a substantial number of Conservative MPs still feel that grammar schools are vital to social mobility and should be part of the UK’s education system. At the time, the then-shadow Europe minister Graham Brady felt so strongly that he resigned from his party’s frontbench. He now chairs the 1922 committee. He told me earlier that he regarded the proposed expansion in Kent as “eminently sensible”. He went on:

“This is a very small step in the right direction. The creation of these satellites in areas where there is evidence of a demand for more grammar places meets some of the unsupplied demand."

However, he doesn’t think creating more grammar schools is inconsistent with the coalition’s policy of allowing more choice and local control over education.

“The overall goal is to allow more choice, more diversity and more local determination of the kind of schools that people want. So far, the government has maintained an illogical exception by keeping Labour’s prohibition on any new grammar schools no matter how much communities want them.”

His fellow Conservative MP Gareth Johnson, who secured a Westminster Hall debate on grammar schools last year,  echoed Brady’s sentiments. He said:

“It makes perfect sense to me to allow good schools to expand whether that is on an existing site or on a ‘satellite campus’. Grammar schools provide social mobility and opportunities for thousands of children. I do not claim that grammar schools are right for every child. Some children flourish is a very academic school and others do not and grammar schools play a vital role in a diverse education system. Having a ‘one size fits all’ system should never be our goal."

The issue of grammar schools is one of those blue-touch paper issues for Conservative backbenchers. As Brady's resignation in 2007 demonstrated, they’re prepared to fight hard for what they see as an important route to social mobility.

A Department for Education spokesman, responding to this afternoon's vote, stated: "The overriding objective of this government's reforms is to increase the supply of good school places so parents have real choice. That includes making it easier for good schools - grammar or otherwise - to increase their published admission number.

"Legislation prohibits the establishment of new grammar schools, and ministers have been clear that that will not change."

Whether or not grammar schools help bright children from less-affluent backgrounds on to better things is a matter that is very much up for debate, but this vote in Kent isn’t a product of such an open discussion.This stealthy expansion of grammar schools is an attempt by the coalition to have things both ways.

Tags: Conservative Party, David Cameron, David Willetts, Gareth Johnson, Graham Brady, Grammar Schools, Rob wilson