The Ofsted squad which turned up at the JFS campus in Kenton, north-west London one morning in July 2014 took the school by surprise. Ranked as an outstanding school and enjoying an excellent academic reputation, JFS had not expected to be the subject of an unannounced inspection.

The investigation had been triggered by a number of complaints to the inspection service. Among the things Ofsted wanted to know was whether the curriculum prepared students for life in modern Britain and prevented "extremist behaviour".

This was around the time of the so-called Trojan Horse inquiry into alleged Islamist radicalism in schools in Birmingham. Inspectors must have wanted to appear even-handed, although they denied targeting faith schools.

At JFS, inspectors "found no evidence to support the concerns raised in a letter to Ofsted claiming students were being indoctrinated by the extreme Orthodox views of some teachers".

Pupils generally felt that incidents of bullying were dealt with effectively and that there was no evidence to support "more serious" allegations about the safeguarding of children.

Staff felt like cogs in a machine being told to do this, do that

But their report caused widespread dismay, because not only did they strip the school of its outstanding status, they rated it below "good" and said that it "requires improvement".

Although teaching remained good, sometimes outstanding, and children performed consistently above the national average in exams, inspectors identified other concerns. The school's leadership did not monitor attendance and disciplinary records well enough.

The "very small number" of students with disabilities or special educational needs, although making better than average progress in English and maths, performed more variably in other subjects. This contrasted with Ofsted's report of five years earlier which noted that students with learning difficulties at JFS were then making outstanding progress.

In addition, the "small number" of lower-ability pupils were judged in 2014 to have made less progress than similar students in other schools.

The use of disciplinary measures was found to be inconsistent. More pupils were ending up in the detention room with the Orwellian title, Room 17. Inspectors reported that in one year one group those sent to Room "17 included a "disproportionate" number of less advantaged children (those eligible for free school meals).

Nothing has been said to link this week's resignation of head teacher Jonathan Miller to the repercussions of the Ofsted report. But it certainly must have added to the pressures of the job of running not only Britain's largest Jewish school, but one of the country's largest overall, with more than 2,000 pupils.

Like his predecessors, Jo Wagerman and Ruth Robins, Mr Miller had been an internal appointment to the top job. But the two women who stamped their personalities on the school had been tough acts to follow; Mrs Wagerman was recognised for her educational achievements with an OBE, Ms Robins was made a Dame.

Stung by Ofsted, the school pressed into action. By the time of a follow-up report in December 2014, the senior leadership had been restructured and an independent "improvement adviser" drafted in to offer guidance.

While improvements had been"encouraging", Ofsted said, the challenge remained to apply them consistently across the school before the next inspection (which is due within the next couple of months). Though many students displayed good attitudes to learning, this was "not always the case," the follow-up report stated.

The reviewing inspector clearly remained bothered about the use of Room 17, saying that the school needed to make sure that disciplinary action was "appropriate to the misdemeanours committed and age of the student".

In lieu of any detailed reason for Mr Miller's departure, speculation has naturally flourished. But one claim doing the rounds on the internet that there had been a power struggle over the school's religious ethos was dismissed out of hand by a source at the school, who said that JFS remained a United Synagogue school and was working closely with the US and the Office of the Chief Rabbi.

The effort to address Ofsted's criticism has put extra demands on teachers, one of whom said that staff felt like "cogs in a machine being told 'do this, do that' ".

JFS is not immune from the national shortage of teachers which makes life more difficult for those left to fill the gaps.

While JFS has been proud of grooming of head teachers from within its ranks, it is likely that governors will look outside for the next permanent head to take the reins in a year's time.

But if recent events have proved unsettling, another good round of exam results this summer will go some way to reassuring parents, no matter who is in charge.