Most teachers stop improving after two or three years in the job, according to a leading academic.
For the first few years in post, most teachers improve rapidly but then they stop improving altogether, says Dylan Wiliam, emeritus professor of education at the Institute of Education, University of London.
"People make claims about having 20 years' experience but they really just have one year's experience repeated 20 times," he told TESS.
Expertise comes as a result of at least 10 years practising what you don't know how to do, continued Professor Wiliam, who spoke last week at a Tapestry Partnership conference, Glasgow, on school improvement.
Chess players who became grand masters and violinists who turned professional became better than the good players because they practised. "Talent is overrated," said Professor Wiliam.
Music professors at the Academy of Music in Berlin conducted a study to see what made the difference between the good violin students and the best. By the age of 18, the best players had accumulated 40 per cent more practice than the good ones and they practised the things they did not know how to do - termed "deliberate practice" - he said.
"That kind of practice is not enjoyable or fun but hard work. What we need in teaching is people who are passionate enough to put in the time and to practise.
"There's no point in us selecting teachers on what we can train them to do - what we can't teach teachers is passion. The question we need to ask every person wanting to enter the profession is: 'Why do you want to be a teacher?' If they say: 'I want to pass on my enjoyment of maths', we should reject them. What we need is that passion for learning," he said.
Teacher Learning Communities, a programme delivered by Tapestry in partnership with Professor Dylan Wiliam, are to be further developed under a new model of master's level CPD at the University of Aberdeen.
Professor Do Coyle, head of the school of education, told delegates that work had started in September on a collaborative programme which will be delivered online.
TLCs, created by Professor Wiliam, involve teachers observing each other's practice and supporting each other as they seek to embed formative assessment techniques in their classroom practice.
Aberdeen's new programme will use the content developed by Tapestry and seek to deepen teachers' understanding through professional enquiry and enhance their leadership of learning skills.
Professor Coyle said that she hoped it would allow teachers to share practice across schools as well as within schools.