A small series of photographs lines a wall in Elizabeth Garrett Anderson School’s reception. In the pictures is Michelle Obama, vivid in blue against the grey of the schoolgirls’ uniforms.

The US First Lady is shown hugging pupils from the North London girls’ school one by one. In the foreground, a pupil is captured wiping away a tear after being embraced by President Barack Obama’s wife.

It is a startling response to meeting a politician’s spouse. The scene has something almost divine about it, as if the child has been greeted by Mother Teresa, or perhaps one of today’s generation of deities - Beyonce, for example.

Yet it was because of the welcome Michelle Obama received that an unlikely, but now very special, relationship has been established between her and the Islington school, which culminated earlier this year in a dozen pupils being invited to visit the White House.

What initially appeared to be a mere publicity stunt for one half of the Obamas has become a tremendous source of motivation for pupils at Elizabeth Garrett Anderson School (EGA) and, it has recently emerged, for Michelle Obama herself.

The story begins in 2009, when the First Couple made their first state visit to the UK. One morning, pupils at EGA were rather cryptically told that a politician’s wife would be attending that day. But when the motorcade of police vehicles and blacked-out people-carriers arrived outside the school gates, it was clear that this wasn’t just any old backbencher’s other half.

“We didn’t know she was going to come because we were told it was a surprise,” says Khadija Bilqis, a Year 10 pupil at the school, who was in Year 7 at the time. “Of all the people it was Michelle Obama. It was amazing.”

Her arrival sparked a frenzy of excitement at the school; gasps and screams from pupils gave the impression that they were meeting a film or music star. It is unlikely that Samantha Cameron or Sarah Brown, former prime minister Gordon Brown’s wife, would have evoked anything like such a response.

And the reason for this was simple. As one half of the first African-American couple to occupy the White House, Michelle Obama is a palpable piece of history, the importance of which was not lost on the pupils.

“Her speech was inspirational,” says Ece Emin, also in Year 10. “She said she could relate to us and that education was key to our future. She said it was cool to be smart.”

In her speech, Obama spoke of her own experience growing up in a working-class neighbourhood in Chicago. “I want you to know that we have very much in common,” she said to the pupils that day. “There was nothing in my story that would land me here. I wasn’t raised with wealth or resources or any social standing to speak of.”

It was during that school visit, while giving her speech, that it dawned on Obama what role she was meant to play in her position as First Lady. According to Jodi Kantor, author of The Obamas: A Mission, A Marriage, the visit was a turning point for her. “She looked at the girls looking at her and saw herself through their eyes, noticing how they hung on her every word,” writes Kantor. “She saw the responsibility, the impact, the potential, of her role. Her time in the White House had been isolating, yet now across the Atlantic she felt so connected.”

Not just a chance encounter

But the relationship between Obama and EGA did not begin by chance. The work EGA does to improve the life chances of its pupils meant it was the perfect choice for Obama’s visit.

The school is a typical central London comprehensive. Its pupils come from a myriad of backgrounds and live in a community where extreme wealth sits cheek by jowl with grinding poverty. More than two-thirds of the girls speak English as an additional language and more than half receive free school meals. Yet its pupils succeed, with nearly 50 per cent meeting the government’s benchmark of five good GCSEs including English and maths. And the school has an “outstanding” judgement from Ofsted to boot.

Indeed, beneath the photographs of Obama in the school’s reception are pictures of former pupils who have gone on to study at Oxford and Cambridge, which act as constant reminders to current pupils of what is possible.

It was for all these reasons that the school was chosen to host the First Lady, says EGA headteacher Jo Dibb. “It wasn’t just a chance encounter; it was because of our ethos,” she adds. “We’re very special in many ways. We have girls, many of them without the advantages of pupils in other parts of the country, that are bucking the trend. So there was a reason Mrs Obama came to our school; we weren’t just picked out of a hat.”

But although the school is succeeding against the odds, there is little doubt that Obama’s visit has had a galvanising effect on the pupils. After the initial visit in 2009, Obama strengthened her bond with the school by inviting 35 pupils, chosen by the senior leadership team, to visit the University of Oxford in May last year.

The girls spent an entire day with the First Lady, herself a graduate of Princeton and Harvard, at Christ Church, Oxford, in what was described as an “immersion experience” to give pupils a taste of life at one of the world’s best universities.

“She made the effort to travel from London to Oxford, which is pretty phenomenal, and the trip was incredibly inspiring for the girls,” says Dibb. “The girls who went were those who we felt had potential, but may not have realised that Oxford is a place for them if they so choose.”

In her speech that day, Obama gestured to the buildings surrounding the pupils and urged them to consider a place at Oxford as their birthright, just as much as it is for those attending Cheltenham Ladies’ College or Roedean. “I’m not the only one that’s excited to see you all here today,” she said. “Students and faculty at this university were eager to visit with you all as well. And there’s a reason for that. It’s because all of us - and it’s important for you to know that - all of us believe that you belong here; that this is a place for you as well.

“We passionately believe that you have the talent within you, that you have the drive, you have the experience to succeed here at Oxford and at universities just like it across the country and across the world.”

Such an endorsement from one of the world’s most influential people could only have given those pupils greater impetus to succeed. But it was arguably Obama’s most recent intervention that most inspired EGA’s pupils. An invitation was sent for 12 girls to join the First Lady at the White House, as guests of the Obamas during Prime Minister David Cameron’s visit last month.

Journey to the White House

The school staged a competition for girls in Years 9 and 10; 200 entered, answering questions on leadership and inspiration. From there, a dozen were picked and flown to Washington, where they visited the White House on three occasions, meeting some of the most powerful women in the US.

“It was mind-blowing,” says Year 9 pupil Micah Dawey, still on a high from the experience.

The pupils listened to the life stories of several female members of staff at the White House, such as the first female head chef, who was preparing the state banquet, and a number of women diplomats from the Department of State.

Speaking to Obama, however, was what had the biggest effect on the girls. “She said we should always push ourselves,” says Nishat Tasmin, also in Year 9. “I think we all had ambitions to go on to university, but after meeting her she gave us more of a push to do it.”

The pupils and their teachers were offered front-row seats to see the President welcome the Camerons, and were given the chance to meet and greet the two world leaders.

And according to their headteacher, the girls have come back different people. “They have developed self-confidence and remarkable self-purpose - more than they would have before,” says Dibb. “All the girls had ambition, but they didn’t all have a clear idea of how to get there. Now they have that purpose.”

Whether the link between Obama and EGA is maintained remains to be seen, but it would be foolish to rule it out. Obama said she saw herself in the pupils of the school. No doubt she will want to see them succeed.