Plans to create more parental choice in the state school sector will cause "chaos" and admissions "gridlock", says the biggest teachers' union.
Teachers' union says schools shake-up is "pandering to middle classes"
The National Union of Teachers, responding to a forthcoming White Paper, says the plans are "pandering to the pushy middle classes".
The government wants more diversity in the school places on offer.
The union's general secretary, Steve Sinnott, says schools would benefit more from a "period of calm".
The teachers' leader was attacking the government's proposed shake-up of the state education sector, announced by the Prime Minister Tony Blair.
A White Paper, due to be published on Tuesday afternoon, will outline plans for schools to become self-governing and for parents to have a wider range of school choice.
It proposes that parents will be able to play a wider role in running schools - and that parents' groups, businesses and other organisations should be able to set up schools, even in areas where there are already surplus places.
The National Association of Head Teachers said the "underlying aim is entirely laudable" but said it was "not clear how increased parental involvement will be delivered and what impact that will have on existing governing bodies".
But the NUT leader attacked the plans as impractical and undesirable.
Mr Sinnott warned that the "proposals will lead to chaos in admissions and planning grid lock".
"Its obsession with choice ignores the fact that parents operate on a far from level playing field. It is pandering to the pushy middle classes at the expense of children in less advantaged circumstances.
"Allowing parents to set up schools regardless of existing capacity in an area will undermine provision for all. But where are these parents going to come from? Currently too few are willing to serve as school governors let alone establish and run new schools.
"What parents want is high-quality education from their local school," he said.
Mr Sinnott also argued that schools have already had the option to become self-governing "foundation schools", but that "few schools have been interested in going down that road".
He also accused the prime minister of basing national plans on the experience of London schools - "ignoring the needs of children and parents in our towns, rural areas and other cities".