School inspectors have voiced serious concerns about behaviour and safety at JFS, Britain’s largest Jewish school.

JFs was downgraded from “outstanding” to a “school that requires improvement” following an unannounced Ofsted inspection.

In their report, published this week, inspectors found that “behaviour and safety require improvement. A minority of students do not demonstrate consistently positive attitudes towards learning across all subjects and teachers”.

They also criticised the way teachers disciplined pupils. “The school’s behaviour policy is not applied in the same way by all staff. Sanctions are not given in a fair and consistent manner and are being used too frequently by some teachers”.

The attendance of the some students was below average, the inspectors said.

Ofsted made its inspection in July after receiving complaints about the school.

It said that inspectors had observed 34 part lessons taught by 34 teachers in total and held discussions with JFS head Jonathan Miller, as well governing chair Michael Glass, its vice chair of governors, and two representatives from Harrow Council, including the local authority designated officer for safeguarding.

They also reviewed a survey answered by 257 parents, and 123 staff questionnaires.

In a letter sent to parents last week, Mr Glass said that governors and senior teachers were “profoundly disappointed”..

Mr Glass said: “in reaching its conclusions, Ofsted has given disproportionate emphasis to issues which do not go to the heart and soul of the school and has not portrayed accurately the school or given appropriate weight to the rich and varied educational experiences provided for our students”.

He said the school had tried to learn more about the nature of complaints that prompted the inspection, but had not been provided with more detail, adding: “We have drawn a number of our own conclusions about the nature of the complaints from some of the comments which Ofsted have made in their report.”

When it was last inspected in 2009, JFS was judged “outstanding” in all categories.

The largest Jewish school in Europe with more than 2,000 students, it continues to perform well academically and had a record 16 Oxbridge offers this summer. The report acknowledged students’ high performance, but added that “the small number of lower ability students, disabled students or those who have special educational needs, and students who are eligible for the additional pupil premium funding, do not achieve as well as other students at the school”.

Mr Glass noted that “despite Ofsted’s concerns about behaviour and safety, the parents’ survey showed that 99 per cent of parents said their child feels safe at JFS and 96 per cent of parents said the school makes sure its pupils are well behaved.”

He added that this year’s GCSE and A level results had been unavailable to Ofsted inspectors in July and were not taken into account when preparing its report.

The school made clear that the new Ofsted grading would not affect its funding.