), Sam Freedman, head of research at Teach First and a former policy adviser to Michael Gove, writes that the imminent decision about whether to allow Weald of Kent Grammar School in Tonbridge to open an "annexe" 10 miles away in Sevenoaks could have far-reaching consequences.
If the controversial decision goes Kent's way, Mr Freedman argues that "we can expect to see a raft of similar proposals put forward in the remaining selective local authorities".
Of the main political parties, the strongest support for grammars has come from Ukip, which has proposed allowing secondaries to convert to grammar status. The Conservatives, meanwhile, have said they would allow all schools judged to be good by Ofsted - including grammars - to expand.
The bottom line
However, since the coalition government came to power in 2010, ministers have been at pains to focus on the most disadvantaged children.
As well as the flagship pupil premium policy - worth pound;1,300 for every primary pupil eligible for free school meals - schools also receive additional financial support for pupils with low prior attainment, those with English as an additional language (EAL) and children from deprived backgrounds. Collectively, these can add tens of thousands of pounds to the budgets of schools serving the most disadvantaged communities.
Grammar school leaders say they are disproportionately losing out as a result of the policy shift, which they argue has exacerbated existing geographical variations in funding.
Paul Evans, headteacher of Colyton Grammar School in Devon, said the changes hit schools that predominantly served pupils who did not qualify for additional funding. Up to pound;2,000 per pupil was available to schools in the most deprived parts of the county, in addition to the basic allocation of about pound;4,600 at key stage 4, he said. By contrast, Colyton Grammar faced a projected deficit of pound;170,000 in two years' time.
Mr Evans said the school had been forced to axe A-level music as a result of a "steep reduction" in its budget, with German also at risk of being scrapped. "I think there is a balance to be struck. I don't think anybody has looked at what the bottom line is and asked if we have moved it too far," he said.
Barry Sindall, chief executive of the Grammar School Heads Association, said that although local authorities should take pupil premium funding into account when allocating resources to maintained schools, this was not always the case. As a result, he said, extra funding for low prior attainment ranged from pound;36 to pound;3,200 per pupil across the country and for EAL students it ranged from pound;47 to pound;4,500.
`Distorting the system'
Mark Fenton, headteacher of Dr Challoner's Grammar School in Buckinghamshire, said children from deprived backgrounds were being supported by both the pupil premium and a much higher level of deprivation funding.
"There are several schools that are going to hit the buffers in the next couple of years," he added. "They are not funded to the level where they can continue to exist."
Charlotte Martin, headteacher of Rugby High in Warwickshire, said this would be the third year in a row that her school had been forced to make redundancies to balance the books.
"There are inequities of funding that have existed for a long time, and on top of those we have decisions that effectively double- or triple-fund deprivation.and that is further distorting the system," she said.
But Ian Widdows, a founder of the National Association of Secondary Moderns and deputy headteacher of Giles Academy in Boston, Lincolnshire, defended the funding's focus.
"If there are additional resources required for students with additional needs, that's just the age we are in," he said. "When you have extra funding for disadvantaged pupils from the pupil premium, it's pretty clear that grammar schools are not going to attract that funding because they tend to be stuffed with middle-class children."
Conor Ryan, director of research at the Sutton Trust education charity, cited the King Edward VI group of five grammar schools in Birmingham, which had doubled its intake of disadvantaged pupils within a selective system.
There was a financial incentive for grammar schools to give priority to disadvantaged pupils, he said.
`Funding should be allocated fairly'
Mark Fenton, headteacher of Dr Challoner's Grammar School in Amersham, Buckinghamshire, says he has been forced to withdraw business studies at both GCSE and A-level, as well as A-level music.
Drama and language A-levels are now at risk, he adds, and the funding squeeze also means the school now has a ratio of 18.7 pupils per teacher, compared with a national average of 15:1 in secondaries.
"Schools have just about got by, but we've got to the point where we can't cut any more," he says.
"I'm not saying that all schools should get exactly the same amount of money but funding should be allocated on a fair basis."