Ruth Kelly, the Education Secretary, has overturned her predecessor Charles Clarke’s controversial plan to make all schools take their fair share of unruly pupils this year.

Mr Clarke, now Home Secretary, wanted every head teacher to have arrangements in place by September for taking on pupils who have been expelled. But Ms Kelly has decided to give schools two years' "breathing space" before they have to take on this added responsibility.

The move - described by the Conservatives as a "cynical ploy" to avoid political fall-out - came as Ms Kelly announced a "zero tolerance" approach to even low-level disruptive behaviour in classrooms.

When Mr Clarke set out his plan last year it sparked accusations that he wanted to use good schools as "a dumping ground" for the problems of bad schools. Mrs Kelly told head teachers in Blackpool that the admissions protocols "need not apply to excluded pupils" until schools are ready.

She said: "I am giving this additional breathing space on the clear expectation that all secondary schools should be part of such agreements by September 2007." The Government said the plan for schools to take their share of other "hard-to-place" pupils, such as children in care and asylum seekers, still applied for this year.

Mrs Kelly's announcement came as both Labour and the Tories set out their rival pledges to get tough on school discipline. Her "zero tolerance" approach includes repeatedly sending Ofsted inspectors into schools with serious behaviour problems.

Other measures announced by Mrs Kelly included sending behavioural experts into problem schools and a renewed drive to issue parenting orders under which courts can fine adults and require them to take lessons in parenting.

Mrs Kelly said the proposals were aimed at cutting low-level bad behaviour, such as talking in class and and using mobile phones.

She said: "We need to re-draw the line on what is acceptable. Good schools already have a strong school ethos and a policy on behaviour that's respected by the whole school community because it's clear, consistent and rigorously applied. This approach must be in every school with any level of bad behaviour dealt with promptly and appropriately.

"Equally, pupils who lack respect for themselves, respect for their classmates, and respect for their teachers need to be made to take responsibility for their own actions. Parents, too, must support the school's behaviour policy and not automatically assume, when their child is punished, that their child must be in the right and the school in the wrong. Every pupil and every teacher has the right to expect a safe, secure and orderly classroom, so that teaching and learning can flourish."

Earlier in the day the Conservatives set out their rival pledges on school discipline. They said they would put £200 million into new "turnaround schools" for disruptive children, taking them out of mainstream classes. Michael Howard, the Tory leader, said: "We are caught in a downward spiral - bad behaviour undermines standards and poor standards encourage bad behaviour."

Mr Howard called for an end to the the present appeals system for those expelled from mainstream schools. This undermined headteachers' authority and gave a "green light" for those allowed back to misbehave, he said.

The Tory proposals also include: giving teachers protected legal status so they can enforce discipline "without fear of having their lives ruined if a child alleges abuse"; giving schools the money and power to introduce CCTV, random drug testing and metal detectors; and enforceable contracts between parents and schools giving headteachers the right to impose discipline.

The Conservatives described Mrs Kelly's decision to give schools more time before imposing unruly pupils on them as a "U-turn". Tim Collins, shadow education secretary, said: "This is a breathtakingly cynical ploy by the Government. Ministers will still force schools to take disruptive pupils - guaranteeing a thug in every playground - but shamelessly hope to get some credit by postponing this daft and dangerous idea until September 2007."

Headteachers said that Mrs Kelly's plans for extra Ofsted visits would not help. David Hart, general secretary of the National Association of Head Teachers, said: "Ofsted must not be used as a stick to beat schools with when schools are doing their best to deal with a hard core of disruptive pupils."

John Dunford, general secretary of the Secondary Heads Association, welcomed the "strong support" from both political parties but also criticised plans for follow-up Ofsted visits. He said: "Where inspectors find discipline problems, the emphasis should be on the support that she mentions, not on more inspection."

He said the Tory plans for "turnaround schools" would put "too many disruptive pupils in one institution, to the benefit of none of them".

Phil Willis, Liberal Democrat education spokesman, said pupil behaviour would get worse if the Government insisted on creating a "culture of fear and hostility in the classroom". He said: "Both Labour and the Tories have given up on trying to eliminate indiscipline in our schools. They are just waiting for bad behaviour to arise, rather than tackling its causes.

"It is essential that all schools develop consistent policies for good behaviour, agreed with parents and students and applied in an even-handed way. "The key to tackling indiscipline must lie in smaller class sizes, which allow teachers to give more time to every child, and an interesting curriculum that pupils want to learn. A culture of fear and hostility in the classroom will only exacerbate the problem."

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