London’s public spaces are well equipped with bronze soldiers and statesmen, royal figures and robber barons, poets and public benefactors.

But there are few children other than Peter Pan - and he never grew up.

Now a newly-cast boy and girl have appeared just south of London Bridge.

They stand outside a 300-year-old school in Bermondsey where children step out into the 21st century from a place that has seen more than 100,000 days of learning.

The sculpture is a delightfully playful and thoughtful response to a school tercentenary. The girl is entwined in two large zeros while the boy reaches out to share a curving figure three. In his other hand he is holding a book, his head slightly turned and raised. Neither figure is a portrait, more an embodiment of the idea of time and childhood. It has the feel of a climbing frame; you can imagine future generations crawling through the lower zero, swinging their scarves over the other numbers and treating it as a meeting place, somewhere to hang out, literally, and gossip. It’s a public statement couched in happy, informal language.

The German-born sculptor, Gerda Rubinstein, has an enviable public record.

Fifty years ago she put a work featuring a running boy into a park in Amsterdam; it is still a gathering point. More recent pieces brighten Tesco’s supermarket in Lewisham, south London, and a hospital in Dudley, West Midlands. Now a grandmother in Blackheath in the London borough of Greenwich, she enjoyed this commission and its challenge. “Art should be liked and it should have a function. If not, it will invite graffiti,” she says.

She knew early on that she didn’t want the Bermondsey sculpture to be on a plinth, but to be entirely touchable, stretched amicably along the school building rather than imposing its presence against it. “The school and the children need one another,” she says.

The Cathedral school of St Saviour and St Mary Overie (to give it its full name) was founded in 1704 by benefactors concerned for the poor children of the neighbourhood. Originally situated “in a dark alley”, it had to temper its charitable impulses to the harsh facts of economic and social deprivation. Diligent ex-pupils might have expected to find work in trades connected with the river, as apprentice oar makers, ships’ carpenters or fishmongers. Few books were available apart from the Bible, and pupils often ran off to do errands for parents or scavenge in the mud of the Thames.

Over the next 300 years, the school maintained a sometimes precarious existence. One master was imprisoned for debt; another “intoxicated himself and ruined his health”. But as London expanded, this small educational nook began to flourish. In 1851, when Charles Dickens was describing the hard lives of neglected local children, exemplified in the tale of Oliver Twist, 183 lucky pupils were taken to Hyde Park to see the Great Exhibition. New buildings were constructed and, by the time of the First World War, there were nearly 400 children on roll. In 2004, that number has steadied at about 240, and the school consistently finds a high place in local education authority league tables, while its intake represents the full range of inner-London cultures and backgrounds.

Chrystal Adams, Hannah McLoughlin, Trent Boxall-Carthew, Moetaz Osman and Amos Eretusi all featured as models in Gerda Rubinstein’s initial set of photographs. Now they’ve plenty to say about the tercentenary. “Hardly any schools are as old as us.” “It can be a bit creepy, thinking about all the people who came here who have died.” “There was a boy in the 18th century who threw a dead cat at a posh girl, but he got forgiven.” “I wouldn’t like to be poor then, you’d be lucky to live past your childhood.” “I like the thought of being in a sculpture; Gerda took bits from all of us, so some of me will always be here.”

Sylvia Morris, the school’s head, is proud of a heritage that hasn’t been unequivocally happy. “This is a place where people have listened to each other down the ages. I have a sense of continuity and fellow-feeling with those masters who died in service, even the one who went to jail.” And some things haven’t changed. “There were breakfast clubs back in the 18th century. We may have moved on from rote learning, but we didn’t invent kindness.”

Earlier this year, a logbook was discovered in a stockroom. “Finding it was like digging up buried treasure. It freed us from the chains of the national curriculum. Birthdays are important for all of us; this special one has enabled us to think about what history really means, to reach our own roots as a community,” says Miss Morris.

Parent governor Kim Edwards has watched the ways in which the school has developed in the dozen years since her eldest daughter was a pupil. “When you look at the children in assembly, you can see how the school truly represents its neighbourhood. There are gradual shifts in the make-up of our population, with altering patterns of immigration, and the faces in the hall bear witness to that. This is a school for the children of the parish, just as it was in the 17th century.”

The Princess Royal’s unveiling of the sculpture on October 7 marked the climax of a series of celebrations. A lively history is being published, full of anecdote, statistics, commentary and reminiscence. Southwark Cathedral will host a pageant with a role for every pupil (there’s already been a service in the cathedral where the Archbishop of Canterbury, in a purple Ghanaian robe, blessed the oldest and youngest in each class. In their academic hoods, the teachers, according to Amos, “looked like the staff at Hogwarts”).

In his sermon, Dr Rowan Williams recalled the “charity children” from long ago and asked their successors to consider the truth that none of us can learn on our own. Inside the school hall, a plaque from 1713 refers to the “Boyes of ye Parifh”, a reminder that education was once a gift for only half the population. Gerda Rubinstein’s sculpture tells a different story.

School generations are poignantly short, changing every six years, but for decades to come the bronze boy and girl will speak of the memorable experience of learning together.