Unions and local authorities were this week assessing the implications of the ruling in a case which saw Tony Blair’s wife, Cherie Booth QC, represent the family against Education Secretary David Blunkett.

Mr Blunkett had refused to order Southlands School in Kent to overturn its decision not to admit the girl whose father had been convicted of assaulting its head and whose siblings had been responsible for a catalogue of disruption from arson to indecent exposure.

The girl, now aged 12, remains at home after almost four terms, as her parents prepare to take their fight to the Appeal Court.

If the decision stands - there is no date yet for a hearing - it will mark yet another court ruling in favour of schools’ autonomy.

As with Graham Cram, the Tyneside schoolboy whose case reached the High Court a week earlier, the judges found in favour of the headteacher and defended his right to run his school in the interests of all pupils and staff.

That principle will be enshrined in law come next September, when the Tories’ final Education Act comes into force. But until then, the judgments serve as a useful pointer.

The Act will ensure that local authority panels, hearing appeals against exclusions from local authority schools, will have to listen to the views of the school and consider the interests of other pupils and staff and the school’s overall disciplinary policy.

The Government is also planning a shake-up of the admissions system as part of the Education Bill, due shortly.

Southlands head Eamonn Cahill had refused to admit the girl as a new pupil at his school, despite her admittedly “blameless” record at primary, because her father had been convicted of assaulting him in a row over an elder child’s school uniform.

Gillian Shephard, Tory education secretary until May, had directed governors to admit the girl, who cannot be identified because of a court order. But David Blunkett revoked the decision after Labour’s general election victory. Teachers had threatened to strike if she were admitted.

Ms Booth told the High Court the girl was being excluded unlawfully and that Mr Blunkett’s decision was “perverse”. But Mr Justice Harrison ruled the Secretary of State had a power but not a duty to order the school to admit the girl.

In the South Tyneside case, Graham Cram had been admitted back to his school on appeal after assaulting a teacher but was largely taught in isolation after threats of action by teachers. He has been off school since January with stress and his parents wanted him returned to mainstream classes. The court refused.

The past 10 years have seen a growing awareness of parents about their rights to challenge the decisions of schools and local authorities over admissions and exclusions. Appeals over admissions rose by 13 per cent last year to an all-time high of 63,000.

Parents won a notable victory last month in Rotherham, where the council was told by the Appeal Court its admissions policy was unlawful after it was challenged by 10 families unable to secure a place at their preferred school.

The Secondary Heads Association this week welcomed the Kent decision. Bob Carstairs, assistant general secretary, said: “This decision should be overtaken by legislation in September 1998, but we see it as fairly significant. We are inundated on our hotline by schools forced to take children they don’t wish to for one reason or another.”