Conservative leader David Cameron has attempted to calm a row with his own MPs over selection in schools, saying the debate is "entirely pointless".
The Conservatives are to back the government's City Academies
The MPs are angry about plans to scrap Tory support for grammar schools and selection based on academic ability.
Mr Cameron believes middle-class children dominate the grammar school intake, shutting out children from poorer backgrounds.
But some Tory MPs are challenging the change of policy, dubbing it "absurd".
Backbenchers voiced their opposition to it at a meeting on Wednesday, arguing there has been no debate within the party about opposing academic selection.
Backbencher Roger Gale said "I am extremely unhappy and I think he is profoundly wrong in the conclusions he has reached."
Evidence from his Kent constituency showed "grammar schools offer a leg up, offer social mobility to those who would otherwise deny it," he added.
He said the "jury was still out" on the government's academy schools, which were backed by Mr Cameron.
Graham Brady, a member of Mr Cameron's shadow cabinet, told BBC Radio 4's PM: "I don't think it's true to say grammar schools entrench privilege.
"The only reason we don't have more children with free school meals in grammar schools is that there aren't grammar schools in urban areas and certainly I have always supported more grammar schools and more selection where parents want it."
'Sheep and goats'
But Mr Cameron dismissed the MPs' concerns saying: "I think this is an entirely pointless debate."
He said history had shown that establishing grammar schools was "extremely difficult and... often leads to them being very unpopular and they are then got rid of".
He added: "In 18 years of Conservative government, we didn't create a whole big number of grammar schools because parents fundamentally don't want their children divided into sheep and goats at the age of 11."
He repeated his pledge that existing grammar schools would not be abolished.
Earlier Tory education spokesman David Willetts backed Labour's controversial academy schools, saying it should be easier to set up and sponsor such institutions.
Academies are non-fee paying, non-selective state schools, which operate outside the control of local education authorities and have private sponsors.
Mr Willetts also distanced himself from the traditional Tory belief in academic selection, saying it was "fantasy" to say selection at the age of 11, which takes place in grammar schools, could be fair.
He said the Tories could use legislation "left behind" by Tony Blair to push academies further than Gordon Brown, Mr Blair's likely successor, "would ever dare to do".
Mr Willetts told the CBI: "We must break free from the belief that academic selection is any longer the way to transform the life chances of bright poor kids.
"We just have to recognise that there is overwhelming evidence that such academic selection entrenches advantage, it does not spread it."
The willingness of middle-class parents to put time and money into extra tuition for their children meant a fair test at age 11 was impossible to design, he said.
"[Academy schools] are doing well in very difficult circumstances. They show that proper academic rigour should never just be reserved for the leafy suburbs and for prosperous families. We in the Conservative Party back them wholeheartedly," Mr Willetts said.
But to encourage the rapid expansion of academies, he said it should be easier for parents or other groups to set up schools and the requirement for sponsors to provide a minimum £2m should be dropped.
Proposals also include having a single academy contract to make it easier for providers to run a nationwide network of schools, and allowing providers to run schools with streaming and "robust discipline" to show that "even in our toughest areas traditional teaching works".
He also wants to commission independent research into what teaching methods work.
Liberal Democrat education spokeswoman Sarah Teather said the policy change showed that the Tories were "desperately searching for some substance on education".
Meanwhile, left-wing Labour MPs and teachers' unions had hoped Gordon Brown would abandon the academies initiative, which they have branded the "privatisation" of state education.
But on Tuesday, the chancellor gave his backing to the scheme, telling the BBC it was "right" that wealthy individuals "put something back into the community".
At the same time, Education Secretary Alan Johnson said the government would "limit" the number of academies to 400.