More than a third of the strictly Orthodox independent schools which have been inspected this year have been criticised for the quality of their secular education.
In five out of 14 independent Charedi schools so far examined in 2008, Ofsted inspectors have said the secular curriculum lacks breadth or is inadequate.
Although independent schools - unlike state schools - do not have to teach the national curriculum, a change in the law five years ago has brought them under closer government scrutiny.
One favoured by Ofsted: Pardes House has "outstanding features" and a "rigorous secular academic provision"
All the Orthodox schools criticised are boys' schools, since Charedi girls enjoy a more extensive secular education, often sitting GCSEs.
At Keser Torah, a small school in Salford for boys aged 12-15, Ofsted's inspector found the overall education "inadequate" because there was "too little attention given to the scientific, aesthetic, creative, physical and technological areas".
Secular studies at Getters Talmud Torah in Stamford Hill, North London, for boys up to 12, were judged "unsatisfactory" because there was no teaching time allocated to "science, physical education, design and technology or aesthetic and creative areas such as drama and arts".
Two other Talmud Torahs, Toldos Yakov Yosef and the Satmar-run Yetev Lev, incurred similar criticisms over their secular provision.
Another, Chaim Meirim, set up by the Vishnitz Chasidic community, was found to offer a "satisfactory" quality of education overall with "outstanding" Jewish studies. But although its maths teaching was considered adequate and boys were able to become fluent in English - which was not the mother tongue of most of them - the one-and-a-half hours a day devoted to secular studies allowed too little time for science and other subjects.
An inspector who visited another Chasidic primary school in Stamford Hill, the Belz-run Machzikei Hadass, at the end of last year reported that its secular education was "poor".
The tougher inspection regime has caused some concern within the Charedi community, according to one of its leading figures, Rabbi Avraham Pinter, principal of a state-aided Orthodox girls' high school. "The law has tightened up and schools are addressing it. There are ongoing discussions with inspectors," he said.
But one answer was for the authorities to understand how some of the educational requirements of the law were in fact being met within the Jewish studies curriculum. "Jewish studies incorporate many of the necessary lifetime skills," he said. "The Department [for Children, Schools and Families] recognises that. It is working out a strategy how to evaluate it."
An Ofsted briefing paper for inspectors notes that the secular curriculum in some Charedi schools "may only occupy six or seven hours and be largely confined to English, mathematics and some general knowledge: the argument put forward by these schools is that many aspects of secular studies are covered in religious studies".
It continues: "This argument is not without substance, since the study of the Talmud, which is a major feature of religious studies, can involve an encyclopaedic range of subject matter, as well as considerable intellectual challenge, and the development of a range of skills in language and logical thinking. However, few schools have tried to describe formally how Limmudei Kodesh contributes to secular knowledge."
Some Charedi schools are clearly passing their inspections with flying colours. Beis Chinuch Lebonos, a school for 518 girls aged from three to 16 in Stamford Hill, had a "well-planned" curriculum with a "good balance" between Kodesh [religious] and Chol [secular] aspects.
London Jewish Girls' High in Hendon is "outstanding", said its inspection report in March. Pardes House Grammar School for boys in Finchley had "outstanding features" with a "rigorous secular academic provision".
Another school judged "outstanding" this year was the Torah Vodaas, a boys' primary in Golders Green, which offered an "abridged version of the national curriculum".
One Stamford Hill Talmud Torah, run by the Bobov Chasidim, also had a favourable inspection. Its secular curriculum was "comprehensive" and although information and computer technology was not taught for cultural reasons, there was evidence of boys using computers for homework.
There was "practical guidance on becoming dependable members of English society".