A state-aided Charedi primary school in Manchester is planning to split into separate boys' and girls' schools following a Court of Appeal ruling on equality.
Yesoiday Hatorah in Prestwich will take similar steps to those taken by Hasmonean High School in London, which also plans to formally divide into two single-sex institutions.
It follows a court decision in late 2017 that a Muslim school in Birmingham was acting unlawfully by keeping boys and girls entirely apart.
However, Ofsted has told Yesoiday Hatorah, which teaches boys and girls separately, that in the meantime it must do more to enable them to socialise together.
The school, which has some 800 pupils, has applied to become a multi-academy trust which would operate two single-sex schools.
After a recent visit, the inspection service reported it was clear from evidence given by the school the application was progressing.
“In the meantime, boys and girls remain segregated,” Ofsted said.
But although boys and girls received the same curriculum and showed similar achievements, Ofsted said that the school’s leadership had “not put sufficient opportunities in place to allow boys and girls to mix in unstructured times. Segregation at these times is detrimental to pupils and is therefore unlawful.”
As a result, “boys and girls are denied the opportunity to socialise and prepare for life in modern Britain.
“Boys and girls do enter and exit the school building together; they mix when families car-share to bring their children to school. At events such as the school charity fair, boys and girls mingle. However, these are times when pupils are with their families.”
The school continues to be rated good by Ofsted, which said that maths and writing standards at the end of year two were comparable to the national average, although reading was slightly lower.
Its inclusive practice on children with special needs and disabilities was praised.
Ofsted said headteacher Rabbi Jonathan Yodaiken led by example, had high expectations and was ably assisted by an enthusiastic team.