The JFS headteacher has pledged that the pupils who led the “loutish and dangerous behaviour” which caused 300 teenagers to be sent home will be dealt with “in the strongest possible way”.

Jonathan Miller said taking the drastic action of removing all of Year 11 from the school premises had been “necessary, if regrettable”.

Teachers had acted after “muck-up day” – a day where, in many schools across the country, pupils traditionally play pranks before they leave to sit their GCSEs – spiralled out of control. In his email, Mr Miller said that no such tradition took place at JFS.

A “sizeable” number of students were said to have brought fireworks into school, thrown eggs and flour around classrooms, and vandalised school property. Videos of pupils damaging a security fence and road signs outside the school and swearing at Mr Miller were posted online.

Mr Miller wrote: “The escalation of bad behaviour by a number of students was all the more distressing. Their behaviour is an embarrassment to the school, the wider community, their parents and themselves. Those involved will be facing consequences.”

He added: “We will be dealing in the strongest way possible with those who have perpetrated those actions seen by so many.”

Mr Miller continued by stressing his commitment to upholding the reputation of the school.

“I always require of all students at JFS that they behave in an exemplary manner, both inside and outside of school,” he said. “I ask all parents to support me in sharing this message with your children. In this regard, I am grateful for the many, many messages I have received in recent days supporting the school’s response to this unprecedented situation.”

The school’s tough response has received the backing of many of its pupils.

Initially, large numbers of year 11 students spoke of their fury that they had been ejected from school a day before they broke up for study leave without explanation.

One 16-year-old student, who wished to remain anonymous, told the JC: “There was a small minority, maybe 20 or so, who were causing a few problems. There was a small egg and flour fight during break time, and a few people left stink bombs in the corridor. But they decided to punish all of us.”

But comments downplaying the misbehaviour of the 300-strong year group were quickly dismissed by pupils from other years, who complained in their droves to the JC that the school had been misrepresented and was fully justified in taking such serious action.

A 17-year-old pupil, currently in year 12, said: “The reason the students were unable to use the toilets is because they vandalised them.

“The kids were sent home after teachers discovered there were hidden fireworks in the ceiling which were going to be used during the lunch break.

“I think that the school most definitely did the right thing by sending all the students home as, when I was walking around the school, the chaos that was happening was not only unprecedented, but totally obscene.”

Last year’s head boy and girl at the school said in a combined statement: “The magnitude of havoc raged by the year 11 pupils is not very clear at all. But it was much more than ‘just a small egg and flour fight’.”

Students Charlie Hillman, Jonas Dein, Annabel Margarefteh and Rachel Kaye said: “The school had to act fast in order to prevent further damage of property and for the legitimate safety of its staff and students, and so we believe the steps taken by the school were highly appropriate.”

Meanwhile, public outcry over the negative portrayal of the school in the press reached fever pitch over the weekend. Using the hashtag “#IloveJFSbecause” , past and present students took to Twitter to proclaim their support of the school and its hardline approach to the year 11 pupils.