Organisations representing head teachers, governors and education managers have attacked government plans to allow successful schools to expand.
The seven bodies also criticised Labour's proposals to give schools a fast-track to foundation status, allowing them to break free from council control, employ their own staff and set their own admissions.
In a joint statement on school autonomy and accountability, they called for continued collaboration between schools "if all children are to be served well".
The comments follow a survey of 45 heads of successful and popular schools by The TES last week which revealed that two-thirds did not want to expand.
They also came in the week that the political parties geared up for an election, widely expected in May.
Alan Milburn, Chancellor of the Duchy of Lancaster, who is spearheading Labour's campaign, told a conference that the current raft of education reforms would offer the "opportunity of a personalised education and greater parental choice... to those without wealth, and not just those with it".
His comments echoed Education SecretaryRuth Kelly, who told the recent North of England education conference that she took it "as a matter of principle that choice should be expanded where we can".
Allowing popular schools to expand is part of the New Labour mantra of "choice and voice". In education, this means giving parents a greater say in the way schools are managed and greater choice between schools.
The Tory party is also seeking to expand choice and has called its education and health policies "The right to choose". Michael Howard, Conservative leader, said last week:"If you want to improve public services, you need to give choice to parents".
The statement from the seven groups, which include the National Association of Head Teachers and the Secondary Heads Association, said moves towards greater independence for schools had to be balanced with an emphasis on schools working together.
It said that the local community should be consulted before schools were allowed to rush into foundation status, "The transfer of assets from community ownership to the ownership of a school governing body should be considered in relation to efforts to link schools more effectively with their community through the extended schools programme.
"No other procedure in government can so quickly and easily remove a major institution from democratic control," it said.
The seven bodies, also including the Association of Directors of Education and Children's Services, the Confederation of Education Service Managers, the National Association of School Governors, the National Governors Council and the Advisory Centre for Education, are concerned about school expansion.
"It is rarely the case that successful schools want expansion for its own sake," they said.
"They recognise that their expansion could cause problems for other schools and could lead to closure of less popular schools, many of which are in areas of deprivation."
Delia Smith, head St Angela's Ursuline convent school, London, said: "You have to have funding, land and space. You can't expand willy-nilly."
Michael Griffiths, head of Northampton school for boys, Northamptonshire, said: "I think the sheer volume of testosterone at our school is such that I'm not sure I want an ever-increasing number of students.
"If a school grows, others that are less successful will decline. You end up with a two-tier system."