The most significant British education research event of recent times took place in the elegant first-floor drawing room of the Nuffield Foundation's Bloomsbury headquarters on a February day in 1998.
The occasion only received page 11 coverage in that week's TES but, in retrospect, what Professor Paul Black and Dr Dylan Wiliam of King's College London had to tell their audience merited front-page treatment.
Having analysed 600 assessment studies, they believed they knew how schools could push up their GCSE performance by about one grade per subject per pupil. It was not a "magic bullet" strategy, they cautioned, but to their audience it seemed the next best thing.
Their study, Inside the Black Box, claimed that if schools adopted "formative assessment" (now better known as assessment for learning), England could shoot up from the middle of the international maths tables to the top five.
They also said that lower-achieving children benefited most from this form of diagnostic assessment which places heavy emphasis on high-quality teacher feedback (see box).
Their presentation had everything. It held out the "promise" of better results for policymakers and schools. It offered the prospect of a more fulfilling school experience for teachers and pupils because formative assessment can only be practised in a non-threatening environment. And it tossed in one odd but fascinating finding: pupils' performance improves if teachers put written comments on their tests, but grades or a mixture of grades and comments have no effect.
No surprise, then, that Black and Wiliam's findings have influenced classroom practice around the world. This month the Organisation for Economic Co-operation and Development became the latest body to follow up their work by publishing its own study of formative assessment in eight countries and holding a launch conference in Paris.
But how much impact has Black and Wiliam's research had in the UK? Although the findings from a subsequent study they carried out in six Medway and Oxfordshire schools were slightly less impressive - children's GCSE scores improved by about half a grade per subject on average and some classes made no gains - the King's studies have been hugely influential. They have helped to turn opinion against end-of-key-stage summative testing in Wales, where key stage 2 and 3 tests are being phased out. In November, Scotland also announced it was ending national testing up to the age of 14. "The climate has changed," Ernie Spencer, a Scottish academic, told the OECD conference. "Accountability isn't as important as it once was."
Northern Ireland is in the throes of change, too. It is to scrap its controversial 11-plus in 2008 and put formative assessment at the heart of its new curriculum.
In England, however, the Government refuses to ditch key-stage tests. Its critics say that high-stakes testing - especially at KS2 - not only encourages teaching to the test and narrows the curriculum, but damages many children's self-esteem. Formative assessment, on the other hand, aims to build self-confidence.
But the Department for Education and Skills says the two forms of assessment are not incompatible, a point that many advocates of formative assessment concede. Pupils can, for example, prepare for external tests by formative exercises such as creating and answering their own model questions.
Professor David Hopkins, the Education Secretary's chief adviser, joked about the difference between formative and summative assessment at the OECD conference: "When a chef tastes the soup, that's formative assessment," he said. "But when the customer tastes it, that's summative."
But he became more serious when he was later questioned about "over-testing". The KS1, 2 and 3 tests were not burdensome, he insisted.
"In any case, there is a moral purpose behind testing children and helping them to fulfil their potential," he said. "We want to raise the proportion of children reaching level 4 at KS2 and this is where formative assessment will play an important part. We recognised some time ago that it was a lever we had not pulled strongly enough but it is now at the centre of our personalised learning agenda."
The DfES is promoting formative assessment through its KS3 and primary strategies and government statistics suggest the drive is succeeding. More than 80 per cent of secondaries have asked for pound;1,000 and four days'
consultancy to help them develop formative assessment as a whole-school initiative. And they are being supported by 195 lead consultants in local authorities.
But Carol Adams, chief executive of the General Teaching Council for England, says the use of formative assessment is still "patchy" and that teachers need more encouragement to develop this skill.
Her views may irritate the DfES but they are endorsed by some of its own consultants. "It's a real mixed bag," one said. "Some schools are tapping into formative assessment but it's often not a whole-school project. Not enough time and commitment are given to it.
"Much depends on who's responsible for assessment in a school and how much support the senior management team offers. And you find that even though a school may be promoting peer assessment - one element of formative assessment - it can be pretty superficial.
"Children in a geography class will say, 'yes, I now realise I should have a couple of full stops in that paragraph,' when they should be thinking about their geography skills.
"In primaries you see teachers sharing learning objectives with pupils but they don't necessarily call this approach formative assessment."
Local education authority assessment advisers have praised the KS3 guidance but are less happy with the primary strategy materials.
But if take-up of formative assessment is slower than it should be, that is not necessarily the DfES's fault. Formative assessment does suffer by having to compete with many other government initiatives for teachers'
But it is also true that many schools are loath to change their ways. If they have prospered using tried-and-tested methods, why should they change tactics, even if the research is robust? Teachers are often wary of formative assessment, too. As Christine Harrison, a King's researcher, says: "There are centres of excellence in England where schools are using formative assessment very well.
"But some teachers are wedded to summative testing. Maths and science teachers will not get rid of end-of-topic questioning because that's part of their culture."
Many teachers also argue that large classes, difficult children and a crowded curriculum make it unrealistic to give every child the kind of attention that formative assessment can entail.
The OECD study says that all these problems can be overcome and insists that formative assessment is "not a passing fad".
It may be right, but many teachers remain unconvinced. Black and Wiliam's team have already given about 400 proselytising talks to 20,000 teachers.
But they and their teacher converts may have to deliver many more if the promise of Inside the Black Box is to be fully realised.
www.teachernet.gov.uk offers sample lesson plans, case studies, online pupil achievement trackers, links to CPD opportunities and materials describing good assessment practice.www.standards.dfes.gov.ukresearch - the DfES's research informed practice site - carries summaries of recent AfL research written for teachers.Formative assessment: improving learning in secondary classrooms is published by the OECD, priced pound;29, www.oecdbookshop.org
INSIDE THE BLACK BOX. Black and Wiliam's advice:
What works ...
* regular classroom testing and the use of results to adjust teaching and learning rather than for competitive grading;
* enhanced feedback between teacher and pupil which may be oral or written;
* the active involvement of all pupils;
* careful attention to pupils' motivation and help in building their self-belief;
* self- or peer-assessment by pupils, discussion in groups and dialogue between teacher and pupils.
... and what doesn't
* tests that encourage rote and superficial learning;
* over-emphasis on the giving of marks and grades at the expense of useful advice to learners;
* competitive teaching approaches that demotivate some pupils;
* feedback, testing and record-keeping that serve a managerial function rather than a learning one.