Vulnerable children could lose out if the Government pushes ahead with plans to give schools more independence, the chief inspector warned this week.
David Bell's concerns were echoed by peers and by England's biggest teaching union.
The Government's five-year-plan for education will make it easier for schools to gain foundation status, which gives them autonomy over staffing and admissions.
Mr Bell told MPs on the education select committee that this could create "potential policy tensions" with the Government's drive to improve child welfare. The Children Act, passed into law last month, aims to join up education with other public services.
Speaking afterwards, Mr Bell said that the vast majority of schools took the welfare of vulnerable children very seriously. However, he said, that as schools became increasingly independent, some would be less willing than others to collaborate and take on pupils who had been excluded for misbehaviour.
Mr Bell told MPs that teachers sometimes felt relieved when their most disruptive pupils dropped out. "If they don't turn up at school some people think, 'Thank goodness they're not here' because it's less hassle," he said.
The National Association of Schoolmasters Union of Women Teachers, which is in favour of removing disruptive pupils from the classroom, described his comments as a "slur on teachers' professionalism".
The National Union of Teachers said foundation status was "the least accountable model of school governance" and that increasing the numbers with that status would severely damage cooperation between schools.
"The Government's proposals for expansion of foundation status cut across the Every Child Matters agenda," it said.
"A community facility in one school, for example, could be threatened by that school becoming a foundation school and gaining ownership of that facility."
Similar concerns were raised in a House of Lords debate this week on the Education Bill, which contains much of the legislation for the five-year plan.
Lord Dearing, the cross-bench peer whose inquiry into universities transformed higher education, said he broadly supported giving schools more autonomy. He too though was concerned that there was a "tension" between independence and the support of the most vulnerable children.
He added that increasing the independence of schools could also make those in disadvantaged areas lose out to more popular schools in middle-class communities. "I do not want to see communities that need their schools to help regenerate the community and provide integrated services going down the pan," he said.
Lord Filkin, education minister, said the Government was consulting on the potential effects of expanding foundation schools and was looking at the incentives it could give to schools to ensure they cooperated with each other.