Schools which continue to completely segregate boys and girls could find themselves penalised by Ofsted following a landmark ruling.

Three Court of Appeal judges have ruled that the mixed-sex Al-Hijrah school in Birmingham’s policy of separating pupils by gender is unlawful sex discrimination.

Ofsted, which brought the challenge, has previously made it clear that if the appeal succeeded “it will apply a consistent approach to all similarly organised schools”.

It means that state schools which segregate pupils for all areas of their education, including lessons, breaks, clubs and trips, could find themselves given a lower rating by the schools watchdog, and in breach of equality laws, if they do not alter their policies.

It is understood that there are around 20 mixed-sex state schools in England which may be operating strict segregation policies, and they are likely to now be given time to make changes to these.

In their decision, the appeal judges said: “It is common ground that the school is not the only Islamic school which operates such a policy and that a number of Jewish schools with a particular Orthodox ethos and some Christian faith schools have similar practices.”

They said there was “a strong argument” for the Education Secretary and Ofsted “to recognise that, given the history of the matter, their failure (despite their expertise and responsibility for these matters) to identify the problem and the fact that they have de facto sanctioned and accepted a state of affairs which is unlawful, the schools affected should be given time to put their houses in order in the light of our conclusion that this is unlawful sex discrimination”.

“The relevant central government authorities should not pivot in the way they have gone about this without recognising the real difficulties those affected will face as a consequence,” the judges added.

Today’s ruling relates to mixed-sex schools only, and therefore does not impact single-sex schools.