“You cannot appreciate how utterly sad and distraught you are,” said the head of the Lincolnshire secondary where a 14-year-old pupil was fatally stabbed. “It was one moment. One moment.”

“A bolt of lightning,” said his deputy, “which you could never predict.”

In the only interview since the murder almost three weeks ago, the head and his deputy told The TES of attempts to restore calm to the school shattered by the attack.

A 15-year-old has appeared in court and been charged with murder and neither the school, its head, staff, the victim nor the defendant can be revealed for legal reasons.

The incident made the front pages of every national newspaper. Today the journalists have gone and fading bouquets line the circular green in front of the school whose stated aim is “achievement by caring”.

The dark red-brick building is clean and neat and its heavy glass doors open into a pale blue entrance hall. A sweeping chest-high counter dominates the reception area. On it sits a driftwood sculpture, the visitors’ book and three tidy piles of leaflets on coping with a traumatic incident.

The school has been overwhelmed with sympathy and offers of help and advice since the incident on November 4 and a book of condolence, to be given to the murdered boy’s parents, now records 138 names “The messages have sustained us from day to day,” said the head. “I was touched by how aware people are of all the victims of this.”

Immediately after the incident though the head and his 46 staff needed time and space to look after each other.

School bells were switched off to stop pupils moving between classrooms and the students were told in an assembly that they were being sent home - they were not told then that a teenager had died.

By the time the press arrived at the school its 278 pupils had left. But the head had to run the gauntlet. As his wife drove him home, a photographer jumped in front of the car to take photos with a flash “like a massive searchlight”. It felt a siege, he said. He got little sleep that night.

The next day staff met to decide what to do. The head said: “There were people from the local authority and other agencies, who were potentially helpful. People who were very welcome. But the most important thing was to meet as a staff, on our own.

“If any member of staff had not been able to come in, it would not have been an issue,” his deputy added. “But almost every person did as a show of solidarity. It gave people strength.” The head felt it was impossible to open as usual but did not want to shut students out so he arranged two fellowship days for them, teachers and parents to meet in the school for mutual support. Counsellors and a Methodist minister attended.

“Our experience as staff was that the strongest support was from our colleagues,” said the head. “We thought children would get the strongest support from their peers and that turned out to be right.”

The deputy said: “We wanted the two days to be a gentle way of getting back in. The students were so dignified. There were tears but it was not hysterical.”

The head joined the school in January, shortly before its bid for specialist arts college status was approved. “The thing that hit me when I came for an interview was the positive nature of the children,” he said.

“They were polite, mature and respectful.

“I said that I wouldn’t come to the school just to run it, I would come to improve it.”

Standards at the school are below county and national averages. It is described as “popular and successful” by inspectors who say it takes in relatively few of the highest attaining pupils.

After the incident the head wondered whether he could continue, but the support of the staff has given him the strength to carry on.

Six days after the attack the school resumed its routine. The deputy head said: “It was the hardest day of our professional lives. We had a fairly brief assembly without embellishment. Anything else would have been too hard.”

Supply staff who had previously worked at the school were loaned back by neighbouring schools so teachers did not have to cover lessons or have strangers in the staffroom.

On Remembrance Day the school assembly was dedicated to their former pupil.

Afterwards students had 20 minutes in class before heading home; many simply sat in silence. And the school will be closed today to mark the teenager’s funeral.

Alongside the letters of condolence there have been practical suggestions.

One letter came from the head of a school which had coped with a fatality.

It advised that to get back to normal, the Lincolnshire school needed to do normal things.

The deputy head said: “Things aren’t normal, but there is something reassuring about routine, about being able to tell people off for chewing gum.”

MESSAGES OF SUPPORT

“I would like to express my sincere gratitude to you all for the professional way in which the incident was dealt with.” Nicky Maguire, parent of a pupil at the school

“We both want to express our support for you and all the staff at this incredibly difficult time. We admire the way that you have dealt with the situation and the lead you have given to the students.” John and Helen Fell, whose son left the school last year and is now in the army “Thank you for the way in which you have kept us as parents informed throughout this very unfortunate incident. We realise this must have been an extremely difficult time for both yourself, all staff and governors.” Richard and Mary-Anne Drinkel, parents of a pupil at the school

“My deepest sympathy to everybody on behalf of myself as director and my sincere thanks to everyone who helped in any way. There has been overwhelming support from other schools, the local community and across the country.” Dr Cheryle Berry, Lincolnshire director of education and culture