One class, two teachers: is this the way to climb the league tables?

Teachers are working in pairs at one London primary school. Peter Stanford reports on an experiment that has improved results dramatically - and earned plaudits from Ofsted

At the interactive whiteboard, Barry Goulding is only momentarily stumped when one of his year five pupils asks him about the purpose of the pedal on the base of the kettle drum. It's a science lesson but because they are doing sound they've got on to the subject of musical instruments. Meanwhile, away to his right, another group is gathered round Goulding's colleague, Margaret Williams, running through a maths exercise.

Classroom sharing is a familiar enough practice in some primary schools, often to make the best use of older building stock. And team-teaching has long been one answer to the nurturing of pupils with special learning needs. But here, at St Joseph's in west London's Maida Vale, something altogether different is happening. This voluntary-aided primary school has, over the past 15 years, been pioneering a radical educational experiment - the two-teacher system. Instead of 30 per year, they have a one-form intake of around 40 pupils who, from nursery through to year six, have not one but two class teachers.

The results speak for themselves. In June 2005, an Ofsted report described St Joseph's as "outstanding" and drew particular attention to "the very high quality of teaching" provided by its unusual system. This innovation had, the report said, enabled a school where around half the pupils have English as an additional language, and where levels of attainment on entry to the nursery are below the national average, to achieve results that have seen it top league tables for primaries in London and be included in the top 5 per cent of all schools nationwide.

Over recent years there has been, as the headteacher Daniel McDonald relates, a great deal of interest in trying to replicate the St Joseph's experiment, but so far no one else has taken the plunge. "I'm afraid it all comes down to money," explains McDonald, a long-serving, charismatic figure whose leadership won the highest praise from Ofsted. "Whereas most primaries spend between 77 and 80 per cent of their delegated budget on staff, we spend over 90 per cent."

The resulting shortfall in funds available for equipment and other projects is made good by an active parents' association which in the past two years has equipped the school's brand new, state-of-the-art technology suite.

In the mid-1980s, McDonald recalls, his school began to reorganise its budget to employ an extra teacher to float between two year groups to meet new demands in the national curriculum for improved standards in core subjects like English, maths and science. "But because these subjects tended to be done in the mornings, we ended up with two part-time teachers making up that one extra role and it was hard to find staff of the right calibre amongst those prepared only to work part-time."

Instead of abandoning the experiment, however, he decided to push on. "I'd already seen an improvement in standards," he remembers, "and was certain there was more that could be achieved."

With the backing of the governors, he began to introduce the two-teacher system, initially in the juniors, but by 1989 throughout the school. There were additional costs to bear - like extending some of the existing classrooms by relocating toilet blocks. And there were sacrifices to be made by dedicating so much of the budget to staff wages. "But you can have all the interactive whiteboards in the world and they are no good," he says, "without good teachers." St Joseph's has managed both.

How do the staff react to this unusual way of working? Barry Goulding and Margaret Williams have both worked in more orthodox set-ups before. "I wasn't sure what to expect when I arrived five years ago," says Goulding. "Obviously they had told me about the system but it's hard to know how it is going to work out until you experience it.

"One of its strengths is simply the fact of having another adult in the classroom with you. It doesn't lessen the responsibility, but it means you can share it. Teaching can be quite an isolated profession. You and a group of children in a room. Here you are constantly observing and learning good practice from your partner."

It is not, McDonald emphasises, a set-up that suits everyone. "Some teachers like to have their own class and run it the way they want," he says. "We're not the place for them. At interview you have to dissuade them." Williams echoes the point. "I think all teachers at some stage in their career need to be alone in a classroom with a class. It's part of growing up as a teacher."

The St Joseph's model involves splitting the class into larger and smaller groups for core subjects. So while Williams, a maths specialist, will take 30 out of the 40, Goulding will take the10 pupils most likely to struggle to keep up with the rest and give them extra attention. The reverse happens with English. It means that the school does not need to remove children with special needs from the classroom for separate tuition. These can be dealt with in the mainstream. And, at the other end of the spectrum, sometimes it is the higher-achieving children who will make up the small group. "Because you can concentrate special attention on those who might otherwise fall behind," says Goulding, "you can raise the general standard. They are no longer slowing the rest down and with more encouragement can rejoin the main group".

It is one of the benefits of this experiment that appeals to John Bangs, head of education at the National Union of Teachers. "Having two qualified teachers in a class will undoubtedly help those with special learning needs to remain and thrive in the mainstream," he says.

"But although I applaud anything that reduces pupil-to-teacher ratios, one to 20 is still too high. The holy grail, according to all our research, is one to 17. That's when you see a real improvement in standards kick in. And I would also question whether in a group of 10 those pupils who would benefit from individual attention will really get it."

It was the flexibility the system offers, however, that first attracted McDonald. And the stability. If one teacher is called out of class or has administrative work to do, their colleague can take the whole group. Staff absences can be absorbed without recourse to supply. That continuity, McDonald believes, is another factor in raising standards - and in staff retention. St Joseph's enjoys rare stability, with some teaching there continuously for 20 or even 30 years.

The problem for those heads who have visited St Joseph's and been impressed by its example is something of a chicken-and-egg situation. Without evidence of an improvement in standards, parents may not be so willing to dip into their own pockets, but without that money to fill the hole left in the budget by increased staff costs it requires a huge leap of faith to employ new teachers to drive up standards.

Catherine McKeever is interim head of St Joseph's Primary in London's Covent Garden. She has been brought in to tackle poor results at key stage two. "I took two of my staff to the Maida Vale school," she says, "and they were bowled over by the way it worked. We are now trying an experiment here with the two-teacher system in year six three days a week. I'd like to do much more of it, but that is as far as my budget will stretch without the sort of parental support that Mr McDonald has worked to build up." His courage in pursuing his own vision, she feels, is key to the whole experiment.

Are there other downsides? McDonald is the first to acknowledge that the financial balancing act is a constant worry. Two years ago, the local education authority cut budgets - "they never seem to want to reward success," he remarks - and left a £60,000 deficit at St Joseph's. It looked like the system couldn't be maintained. But at a crisis meeting, the parents stepped in and contributed to a special fund which plugged the hole.

It also places an additional burden on McDonald's shoulders to recruit and pair the right teachers to achieve classroom harmony. Sometimes it works, sometimes it is less successful, he admits. And some basic rules have to be observed. Parents coming in for meetings with form teachers must always meet both. And there must be no suggestion that one is senior to the other in the classroom situation. They have to operate as equals.

Goulding and Williams do not talk of negatives but of the compromises that the system can entail alongside its benefits. It can, they say, dampen spontaneity in the classroom. "Barry has been doing some work with play scripts with the big English group this week," says Williams, "and that could easily, if he were on his own, develop into something bigger like an informal staging of a play. But because I'm there with the smaller group, it is harder.

"And it's the same for me. Sometimes I'd like to extend the maths games we do, but you have to be aware of noise and that someone else is trying to do something else in the same room."

However, set against the school's success, these are, they admit, compromises worth making. And it is that success, at a time when all are being encouraged to seek higher standards, that makes the case of St Joseph's both so compelling and so puzzling.

With the government talking of building on successful schools, why hasn't its experiment been copied? If start-up costs are the issue, why not a fund to encourage schools with a big enough catchment area and appropriate buildings to take the plunge? A little encouragement could, on the basis of this example, yield substantial rewards.