Teacher assessment can be as reliable a guide to pupils' achievements as national tests, a study for the Government's test regulator has found.
Research in 91 secondaries using an enhanced form of teacher assessment for English found their judgements of pupils broadly in line with those of tests.
Moreover, it found the new system showed up weaknesses in pupils' learning - and could therefore be used to raise achievement - that the tests had not identified.
The findings support the Qualifications and Curriculum Authority in its battle with the Department for Education and Skills over the future of national testing.
Assessing Pupils' Progress (APP) is being introduced at key stage 3 in secondaries across the country and is about to be piloted in 60 primaries.
Developed by the QCA to measure progress in English, assessment is built into day-to-day classroom activities, rather than work done under exam conditions.
It includes guidelines on how to make structured assessments from normal work in reading and writing and how a bank of tasks can be woven into lessons. They are designed so that teachers can identify which aspects of a pupil's or group's learning needs attention. The material so far prepared includes complete lesson plans.
The QCA claims that the judgements the system produces are both diagnostic and summative; in other words they pinpoint strengths and weaknesses as well as measuring attainment.
A report on the KS3 pilot says that one aim has been "to assess whether indicators of national progress could be derived during the key stage from a teacher's assessment".
Where teachers' judgements differed from test results, teachers tended to be more favourable. But this, said the report, may be because staff can identify attainments that tests may overlook.
The trial also discovered that many schools were not "overtly" teaching reading skills in the early years of KS3, a finding it described as "striking and unanticipated", and which schools were acting upon.
QCA staff are cagey about the potential impact of the new assessment system on tests, but Sue Horner, the authority's head of English, says that the materials should help teachers assess overall progress.
The system is being made available to all secondaries this year, and should be ready for use throughout the primary sector in a year's time.
Lisa Newman, an advanced skills English teacher from Hesketh Fletcher C of E comprehensive in Atherton, Manchester, who has been involved in the system's development since the trials began, says that her school's Sats results had improved by around 15 per cent.
She said: "Until now, teachers have seemed to regard English as something to be assessed intuitively rather than precisely.
"It's great to have this new sophisticated technology which enables you to say to a child 'you've got four of the assessment focuses you need for the level' and agree to target the remaining. It's improving the confidence of the teachers and of the pupils, who are becoming very aware of their skills."
Any move to replace national testing, though, is likely to face opposition from the DfES. In May, Ken Boston, QCA chief executive, said that standardised teacher assessment could replace tests in the long run if it could be shown to be reliable and rigorous.
But he was slapped down by the DfES, which said there was "absolutely no question of moving away from externally marked tests".
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