What’s the most valuable resource any school possesses? Jane Lees, five terms into her headship at Mornington high school, Wigan, Lancashire, has no doubt. “It’s the collective experience of your teachers - the sum total of their commitment and know-how, and their professional satisfaction. It’s a powerful force for school improvement. The trick is knowing how to tap it - how to create a climate where sharing good practice is second nature.”

But she’s realistic enough to concede that it’s easier said than done. For a start, there is a long tradition, especially in secondary schools, of teacher isolation. The “my subject, my classroom, my business” syndrome is deeply rooted, and school design - rows of cell-like classrooms - reinforces it.

Ten years of media teacher-bashing have made matters worse. Teachers willing to share good practice need confidence, something that has been eroded in recent years. “If you’re under pressure,” says a subject co-ordinator, “you keep your head down. You play safe.”

And if you’re unhappy about the Government’s proposals for threshold assessment and performance-related pay, as many teachers are, you may be suspicious of a colleague who wants to watch your lesson.

What happens if your school is already seen as successful and high-achieving? As the deputy head of a big North Yorkshire comprehensive wryly admits, that can be a problem too. “There’s a tradition of autonomy here,” he says, “a sort of closed-down-ness. We’re too complacent. If the machine isn’t broken, we tend to say, why try to fix it?” Jane Lees, and a growing number of heads and teachers like her, recognise the force of these objections. They remain convinced, though, that schools themselves are the most potent forces for improvement. Teachers need to talk about teaching - their own and other people’s.The bonus, if that happens,is that the teachers benefit just as much as the school.It’s the ideal sort of staffdevelopment.

So how do you get there? By consent, they say, and by very easy stages. For Tim Bos, principal of Riverside community college in Leicester (a new amalgamation of inner-city schools), the priority is to boost morale and get new staff to work together. He has established guidelines for everyone to follow - we don’t have to find the truth but we must always seek it; in this school, Relationships (you hear the capital letter in his inflexion) matter; we all contribute to improving this college. Above all, he says:

“It’s OK to talk about teaching and learning. That doesn’t mean talking Ofsted objectives. It means describing what we are doing.”

It is often primary schools, more used to sharing, that take a lead. Putting the literacy and numercy strategies into action has been a powerful stimulus. Sometimes the initiative has come from the local education authority. Newcastle, for instance, identified 10 of its primary staff as numeracy lead teachers and made sure other teachers in the city could visit them in their schools and discuss their lessons with them.

At Low Ash first school in Bradford, West Yorkshire, they take this principle one stage further. Teachers there try out model lessons for each other, watch each other teaching and practise focused lesson observation. “Of course there are reservations,” says headteacher Vivien Kirby.“But this is about having confidence in yourself and your colleagues - having the courage to say a particular lesson wasn’t very good, and shouting from the rooftops the things that go well. It’s the most effective sort of school-based training.”

Lynda Harrison, head of Trinity C of E primary school at Ford, near Shrewsbury, Shropshire, tells a similar story. “We used our entitlement time to bring the local authority adviser into school to work with our two maths co-ordinators.

“Everybody agreed to monitor another teacher and give feedback. That fitted the monitoring and evaluation provisions of the school development plan.

“Now we are looking at whole school issues in other areas, particularly the quality of teaching and learning. It’s good for the school, but it’s useful for teachers too.”

Cynics might dismiss such accounts as just headteacher-talk, and claim classroom teachers see peer observation in a different light. Tony Hinkley, deputy head at Ellowes Hall secondary school in Dudley, disagrees. At his school, systematic observation developed at departmental level first, with the expectation that every teacher would observe a colleague and be observed at least once in every term.

Soon expectation came to be regarded as entitlement. Observation became cross-departmental and began to focus on specific objectives - the use of questioning, for instance - or on whole-school planning issues, such as keeping pupils on task. Now specific development needs are carefully logged, and the school sets out to meet them.

According to Tony Hinkley, the process, which uses supply teachers paid from the school’s existing Standards Fund allocation to cover observers’ lessons, has “opened up a far more positive professional development climate”.

The icing on the cake, he says, is that it has helped to bring about a real improvement in the school’s teaching standards. In 1994, Ofsted reported that 80 per cent of lessons seen were satisfactory or better. When the school was inspected again last year, a striking 97 per cent of its lessons were deemed to have reached that standard. His verdict? “It really makes a difference. Everybody gains. Nobody loses.”