The idea, suggested by its policy review group and also advocated by the Liberal Democrats, could lead to schools competing to take the country's toughest pupils.
But even on the day it was announced in Blackpool, doubts surfaced about the detail. Shadow education ministers told The TES they planned to use postcodes to decide which pupils had the extra funding and acknowledged that in some cases this could lead to more- affluent pupils benefiting.
The announcement came as David Cameron used his conference speech to say that while proud of his Eton education, he planned to send his children to state schools.
But he wanted "schools where they use the tried and trusted teaching methods, not some experimental system of letting you discover the world for yourself."
To achieve this, he promised to make it easier for charities, churches and others to provide the state schools he said parents wanted.
In his debut conference speech, Michael Gove, shadow education secretary, launched the party's Comprehensively Excellent campaign. He explained that it involved analysing the qualities that make the country's top-performing comprehensive a success, so that they could be adopted more widely.
But it is unlikely to offer a wild break from tradition: early suggestions included having blazers, prefects and longer lunch hours.
The Conservatives like Labour last week unveiled few genuinely new education policies, despite fevered election speculation.
Mr Gove repeated the party's plans to protect teachers from malicious allegations and stop heads being overruled by exclusion appeals panels.
He did, however, have a novel solution to gang culture. Why did pupils join them? Because they were "so restricted by health and safety rules that they had never learnt to manage risk". The answer? For teachers supervising "adventurous" school trips to be liable only for accidents if they had been reckless or shown deliberate intent.
It was part of an assault on compensation culture which included a declaration that the party would allow children to enjoy "a world of conkers, yo-yos and snowballs" that set delegates whooping.
Mr Gove played to the gallery. Reassuring traditional Tories who may have been disorientated by last year's green backdrop, touchy-feely speeches and anti-11 plus talk, he spoke against an almost entirely blue background and praised Margaret Thatcher twice within the first three minutes, winning rapturous applause.
"I will always be a Conservative," Mr Gove intoned, before name-checking Disraeli and Churchill.
Colleagues later said it sounded like a leadership bid. It certainly seemed calculated to dispel any idea that he was one of the party's suspiciously regarded modernisers.
However, there were signs in Blackpool that the Conservatives' modernising tendency is still alive.
Stephen Dorrell MP, co-author of the party's decidedly liberal public services policy review, spoke at a fringe meeting of the need to win back teachers' trust.
But as the Conservatives rush to produce a manifesto, The TES understands that much of what the review suggested will be discarded. One of its most publicised ideas to hold back 11-year-olds if they do not progress is only likely to be held as a reserve, "nuclear option".
And the idea of a chief education and skills officer, to improve links with Whitehall, has not gone down well with the front bench. Nor have suggestions of over-testing.
And the 11-plus? It barely figured, with dissent over refusal to back the reintroduction of grammars confined to a fringe meeting.