It was the second night of the St Bede’s away weekend. The dorm corridors were quiet: it had been a busy day and most pupils were sleeping peacefully.

And then the fire alarm went off.

Once, as Oscar Wilde pointed out, can be regarded as a misfortune. But this was the second time it had gone off in two days. Staff from the Bolton primary rushed into the corridor to see what had happened. Eleven- year-old Anthony was standing by the alarm, looking guilty - yet slightly pleased with himself.

June Roberts, St Bede’s deputy head, felt her heart sink. Last night, Anthony’s brother, Ben, had accidentally set off the fire alarm by using hairspray in his dorm.

“Why did you do that?” Mrs Roberts snapped at Anthony.

The boy looked petulant. “Well, Ben did it,” he said. “So I wanted to do it, too.”

It would be hard - if not impossible - to find a school that does not have at least one set of siblings among its pupils. And intense rivalry is often par for the course.

Competition between siblings is one of the most consistent themes of human civilisation. From Cain and Abel, through King Lear’s daughters to Bart and Lisa Simpson, very little can match a good story of sibling animosity. It is one of the reasons that coverage of the Labour leadership race last summer focused so closely on the competition between brothers Ed and David Miliband. Something about two brothers pursuing a single prize captures our collective imagination.

This is certainly true of many siblings, says Steve Mills, deputy head of William Ransom Primary in Hertfordshire, and Primary Teacher of the Year in the 2009 Teaching Awards. One of Mr Mills’s pupils is a budding actor, with a role in a CBBC series. Her brother, two years younger, is not.

“Outwardly, her brother is dead proud of her,” Mr Mills says. “But at home it is a different story. He can be quite difficult: there will be name- calling, playing up. He will compete like mad for attention, bust a gut to do as well as he can at his sport. There is very much a public and a private face of sibling rivalry.”

In the case of Anthony and his brother Ben, however, the public and the private were identical. The boys simply cannot stand one another. “As soon as they open their mouths, they are down each other’s throats,” Mrs Roberts says. “One says `good morning’, and the other says `no, it’s not’.”

Anthony is a talented footballer; this is something Ben does everything in his power to sabotage. He regularly shoves his brother during a match, deliberately starting a fight. And fights often break out between the two brothers over the loyalties of a shared friend. “They were tearing chunks out of each other,” Mrs Roberts says. “They could be charming boys, but then they would change in a flash.”

“Small children haven’t grasped the concept of some qualities being infinite,” says Dorothy Rowe, psychologist and author of My Dearest Enemy, My Dangerous Friend, which deals with sibling relationships. “If brother has more cake, there is less left for you. They don’t grasp that loving more people doesn’t mean your love is diminished. This is then played out in every scene possible. School just becomes the theatre where it’s obvious to lots of people.”

Adult assumptions often form a large part of the problem, and are something of which teachers should be wary. Children are forever being told that they must be so proud of their sister, must really admire their brother. Instead of understanding that their sibling, too, needs encouragement and support from time to time, children hear this as implicit disapproval. “Well done, Jemima” is interpreted as “Jemima’s great, and you’re not”. Similarly, “You should be proud of Jemima” can be misheard as, “Why aren’t you more like her?”

“It isn’t what happens to children that is important,” says Dr Rowe. “It’s how the child interprets what happens to him or her. And we have no control over how children interpret what we do. That is what makes parenting - and teaching - so difficult.”

Ed Miliband has claimed that his only doubt over standing for the Labour leadership was the competition with his brother. “Am I really going to say I am not going to stand because my brother is standing?” he told newspapers. “If he wasn’t in the race, I would not have had any hesitation.”

Mr Mills has seen such doubts in school, too. But primary pupils tend to lack the adult politician’s self-awareness. So instead of confronting their fears and joining the race, they drop out.

Among the pupils at William Ransom are twin boys, both talented tennis players. They both compete in county tournaments; they have both attended elite camps for potential England players. But on several occasions, each boy has pulled out of important tournaments, purely because it looked like the other might do better.

Most recently, one of the twins dropped out of a national final at the very last minute. Then he attended the match and watched his brother win. “He was quite peed off when he got home,” says Mr Mills. “It presented itself as not caring - `bovvered?’ - but, deep down, he was hurting.

“They put this pressure on themselves to achieve. Rather than wanting to have a go, and maybe come second best to a brother or sister, they pull themselves out of the loop, just in case. They want to avoid disappointment.”

Competition between twins - or, indeed, triplets or quads - can be particularly intense. It is sibling rivalry distilled into its purest form: they are the same age, studying the same curriculum, aiming for the same goals at the same time.

But patterns are impossible to predict. This summer, 18-year-old triplets Terrese, Alannah and Cheridan Morgan all took their A-levels at Stoke-on- Trent Sixth Form College. All opted for A-level psychology; Alannah, however, was the only one to achieve 100 per cent in one of her papers.

But in this case there was no animosity whatsoever. “There was never any bad feeling among them,” insists Angela Keane, their psychology teacher. “Though if one of the triplets got good marks, (in the) next assignment the other would get slightly higher. And then the next one. It was interesting. But they wouldn’t fall out. I suppose they were just focused on their own careers.”

Angela Palin has seen similar equanimity among her pupil siblings. The head of St Mellion CofE Primary in Cornwall teaches a girl who, from Year 3 onwards, has been an extremely gifted athlete. She is a particularly talented runner and has represented the county in sprinting and cross- country races.

Then, unexpectedly, her sister began to run. Two years younger, she reached Year 3 and felt that her turn had come. And so she, too, began to try out for county teams. “I think she knew that she was having to measure up to her sister,” says Mrs Palin. “But she enjoyed it.

“She also does horse riding, has other things going on in her life. So it’s not so vital that she is as good as the older one. If she had failed the county trials, there would have been disappointment and acceptance, but no real rivalry.”

Suspending hostilities comes more easily when children feel valued as individuals, says Helen Wright, head of St Mary’s Calne secondary in Wiltshire. “You are not therapists in school,” she says. “But you are there to show each child their full potential, to develop areas they are good at. Treat them as individuals, not as extensions of their brother or sister. Then they see the world in a more balanced way.”

Teachers can also minimise opportunities for gratuitous sibling one- upmanship. Mr Mills taught a girl whose older brother would regularly examine her reading books, to see how her progress compared with his own at her age. The school responded by moving the girl on to an entirely different reading scheme so that her brother was no longer able to taunt her with evidence of his superiority.

Mr Mills also tries to avoid ever mentioning one sibling to another, no matter what the context. Dr Wright does the same. “As a teacher, you are not going to understand totally the family dynamics,” she says.

“It’s very easy for staff to be well-meaning in their praise of a sibling - you are trying to be nice, trying to be kind. But that can backfire, and you may have diminished someone by saying it.”

At St Bede’s, Mrs Roberts is increasingly forced to keep Ben and Anthony apart at all times, to avoid breaktime descent into playground brawls.

When one teacher discovered that Anthony had an unexpected fondness for cleaning, he was nominated for regular “community service”, taking him out of the playground altogether: he now spends breaktimes scrubbing surfaces in the staffroom.

“You just think of things all the time to try and keep them apart,” Mrs Roberts says. “It’s been eminently sensible of their parents to try and send them to different secondary schools, for everyone’s sanity.”

Dr Wright, however, argues in favour of sending siblings to the same school. Aside from the practical concerns, shared memories can prove a bonding point in later life.

But, she adds, parents should not automatically assume that the school that suits one sibling will necessarily suit the others. “You need to think about it for each child,” she says.

“School is a place where individuals can learn to be who they are, not just judged by who other people in their family are.”

*Some pupils’ names have been changed

Brothers (and sisters) in arms

The Miliband brothers are just the latest in a long heritage of famous sibling rivalries:

- Richard I and King John The former’s nickname, “the Lionheart”, says it all. He was viewed as a valiant and warrior leader. His successor and brother, meanwhile, was branded an ineffective autocrat.

- AS Byatt and Margaret Drabble

- Allegedly this sisterly spat began when Margaret wrote about a family tea-set her sister had been planning to use herself.

- Venus and Serena Williams Both have been ranked number one in their game at some point in their career, and they have played opposite each other in a total of eight grand slam finals. But it’s always all smiles for the cameras.

- Liam and Noel Gallagher After years of public spats and cancelled tour dates due to “altercations”, Noel finally left Oasis, saying: “I simply could not go on working with Liam a day longer.”

- King George VI and Edward VIII After his older, more confident brother abdicates, George (Bertie) reluctantly assumes the throne. King George’s battle to overcome his stammer and gain the public’s acceptance is at the centre of Oscar-hopeful biopic The King’s Speech.