The London Oratory School, one of England’s oldest Catholic state-funded boys’ schools, has won a court battle after being accused of “socially selective” admissions rules.

The school, whose pupils have included the sons of former prime minister Tony Blair, Liberal Democrat leader Nick Clegg and deputy Labour leader Harriet Harman, has successfully challenged criticisms from the Office of the Schools Adjudicator (OSA).

The OSA ruled in July 2014 that the school’s admissions arrangements breached national rules. This followed a complaint from the British Humanist Association (BHA) that the school had no arrangements for admitting pupils of no faith.

The BHA also claimed the school’s admissions system was socially selective because “strenuous” faith-based oversubscription criteria were, in practice, socio-economic selection criteria.

However, in a ruling published today, Mr Justice Cobb said the OSA’s decision was “reached by a process which was procedurally unfair to the school”. He said the decision was “flawed” and must be quashed.

The judge said: “While I believe that the adjudicator has, in the main, endeavoured to fulfil his responsibilities conscientiously for the long-term benefit of the school, the candidates and their parents, his approach to his task in the specific respects set out (in his ruling) have in my judgement been shown to be unlawful and/or unreasonable and cannot stand.

“This will be of little comfort to the school which has, I am sure, found this process extremely challenging.”

The school’s solicitor, Ane Vernon, said: “The allegation, which made headline news, that the school was socially selective and discriminating against less well-off families has been hurtful to staff, pupils and parents.

“This damaging allegation has been found by the judge to be wrong and unfair, and the finding vindicates the robust approach the school has had to take against the Office of the Schools Adjudicator.”

Headmaster David McFadden said: “The judge’s decision supports us in continuing to preserve the school’s ethos and serving Catholic families throughout the whole of London.”

However, Richy Thompson, campaigns manager at the BHA, said: “The Oratory still stands as having been found guilty of 99 breaches of the school admissions code.

“The evidence is clear, the school’s intake has consistently been found to be socio-economically skewed and Mr Justice Cobb did not refute the adjudicator’s contention that a degree of social selection of school candidates was ‘inherent’ in the admissions criteria...Nothing has really been resolved with this judgement and much depends on further submissions and clarification.”

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Lotteries should decide secondary school admissions, parents say - 11 September 2014

’The increasing number of faith schools means there is a real danger of creating educational apartheid’ - 5 December 2013