The National Secular Society has called on Ofsted and the Department for Education (DfE) to ensure that all schools teach the National Curriculum in full after the head of a publicly funded Jewish faith school admitted to advising students not to answer exam questions which conflict with the school's strict Orthodox religious beliefs.

The head of the Yesodey Hatorah secondary girls' school has stated that he will "discourage pupils from answering 'halachically questionable' exam questions", according to the Hackney Citizen. This comes after the school was found to be redacting exam questions on science papers following an investigation by the National Secular Society.

After being warned against blacking out exam questions, Rabbi Avraham Pinter said that "if we can't redact [questions], then we won't redact them." However, the Rabbi went on to state that "our children will be aware of which questions they should be answering and which ones they shouldn't be." Pinter also said that evolution was not compatible with the school's strict, Orthodox ethos. It is now clear that rather than redacting questions as they had in the past, the school is advising students not to address the questions.

The schools is now said to be "defiant" over the practice of telling children not to answer exam questions, and the secondary has been downgraded from "outstanding" to "good" after a recent 'no-notice' Ofsted inspection.

The National Secular Society has written to Ofsted Chief Inspector Sir Michael Wilshaw and the DfE raising concerns that the school, and potentially other faith schools, may be failing to teach the National Curriculum in full when scientific facts clash with the school's ethos.

In the letter to the schools regulator and the DfE, the NSS also raise concerns that children's "sexual and reproductive health rights are being impeded by the refusal to teach such key areas of the National Curriculum as human reproduction".

The letter warns that "children are entitled to be taught about these issues in preparation for life, and it is likely that the parents who send children to these schools are materially less likely than other parents to be teaching them this vital information at home."

The NSS has also asked the schools regulator to investigate comments made by Rabbi Pinter which indicate that he regards homosexuality to be incompatible with the school's religious ethos.

In 2013, the National Secular Society revealed that the school was redacting exam questions on topics such as human reproduction and evolution, which did not conform to strict, Orthodox beliefs.

The exam regulator Ofqual subsequently made clear to exam boards that schools should not be allowed to redact questions and that any attempt to do so should be treated as "malpractice".

Stephen Evans, campaign manager at the National Secular Society, said: "advising young people not to answer exam questions clearly isn't in the students' best interests, as it prevents them from demonstrating their ability in the subject they should have been taught as part of the National Curriculum. But the school's attitude clearly extends beyond exams and into science classes, where children and young people are being deprived of vital scientific knowledge.

"We hope Ofsted and the DfE will share our concern that such behaviour by schools could disadvantage pupils by failing to promote their individual autonomy, leaving them ill-equipped for life outside of a religious community, and by denying them the opportunity to reach their full potential.

"This represents the intellectual betrayal of children, whose independent interests are being sidelined by schools more intent on pushing their own religious agenda.

"Unfortunately this is another example of a common problem throughout our state education system – children's education being compromised by the influence of religious organisations. The time has surely come to question the appropriateness religious organisations running publicly funded schools in 21st century Britain."

According to the school's 2010 Ofsted inspection report, all of the Yesodey Hatorah's students come from "strictly Orthodox Jewish homes." A 2013 school prospectus noted that "Charedi homes do not have TV or other inappropriate media. Parents ensure that their children do not have access to the Internet or any other media which do not meet the stringent moral criteria of the Charedi community".