The head of the schools inspection service has defended her decision to penalise Al-Hijrah School in Birmingham for segregating boys and girls.
Amanda Spielman, head of inspection service Ofsted, said the school was just one example of a wider problem.
She said inspectors face “increasing hostility” from a few schools that have been influenced by “the most conservative religious groups”.
And she insisted schools had to teach “British values” because they helped to unite people in a multi-cultural society.
A huge row broke out after Ofsted ruled Al-Hijrah, a council-funded Muslim school in Bordesley, was school was practising unlawful discrimination because it separated boys and girls from the age of nine.
It led to a series of court battles, with judges eventually ruling in Ofsted’s favour.
In a speech to think tank Policy Exchange, Ms Spielman said: “We see in some of the more extreme cases that religious group identity and authority are being systematically built up and used to limit individual liberties, such as the right of a girl to enjoy the same freedoms and opportunities as a boy.
“We made a difficult call in the case of Al-Hijrah School in Birmingham that the segregation practised there infringed the law, and our inspectors’ view was upheld in the Court of Appeal.”
It was an example of “worrying developments in a small number of state schools, as well in some independent schools and in unregistered provision.”, she said.
“We see an expanding sense of religious and/or cultural entitlement to have aspects of a school’s provision dictated by the preferences of a particular group, whether or not members of that group even constitute the majority of a school’s intake.
"This can affect what is taught and what is not taught, what children take part in and what they are withdrawn from, and what children wear or don’t wear.”
And she warned: “We need to recognise that where this kind of pressure builds up, it can not only undermine the authority of a head, but also limit the extent to which schools can help build community cohesion and encourage integration.”
Ms Spielman also said that some faith schools were among the best schools in the country.
She insisted it was better to discuss what was going on in schools openly, rather than allowing extremist groups such as the EDL or BNP to dominate the conversation.
“For many people, the things I have been talking about today are too sensitive and too difficult for them to want to risk giving offence. They are easy things to skirt, yet the risk of doing so is great.
“If we leave these topics to the likes of the EDL and BNP on the one hand and Islamists on the other, then the mission of integration will fail.”