ACCAC, the Welsh qualifications, curriculum and assessment agency, says around 70-75 per cent of Wales's 200-plus secondaries have indicated they will want external marking of the optional tests in 2006. Optional papers will also be available in 2007 but without external marking.
Following the recommendations of last year's Daugherty review, Wales has now abolished all Sats tests. Instead, pupils' progress will be recorded via beefed-up teacher assessment - highlighted as a key contributor to teacher workload in a union survey published last week (TES Cymru, November 25).
But John Valentine Williams, ACCAC's chief executive, said changes to Wales's assessment system should be workload neutral - once they have been fully implemented.
The agency, together with Welsh exam board the Welsh Joint Education Committee, is working on the new assessment arrangements, and expects to start consultations on its proposals in the first half of next year.
Optional KS2 test papers (without external marking) will be available next summer, but by 2007 primaries will be provided with a wider range of optional assessment materials in a package designed to support teacher assessment, said Mr Williams.
ACCAC is looking at moderating KS2 teacher assessments via clusters of secondary schools and their feeder primaries, and is drawing on good practice in Wales for models.
Daugherty also proposed the introduction of skills tests for Year 5 pupils, and ACCAC has been reviewing what tests are already available nationally and internationally - and their effectiveness.
Mr Williams said: "We are moving more towards teacher assessment than tests, so how do these particular tests fit into that bigger picture? Everyone accepts there has to be a greater emphasis on skills development, but how will tests help that?
"We haven't yet reached any conclusions, all options are open."
At KS3, secondary schools will be accredited as having appropriate assessment procedures in place. They could be expected to produce portfolios of a range of pupils' work in every subject, to help verify their systems for teacher assessment.
But teachers will not have to gather portfolios for each individual pupil, and ACCAC is planning guidance on just how much evidence will be needed to ensure a school's judgements about pupils' achievements is fair and accurate.
The assessment changes will dovetail with wider reforms of the curriculum in Wales, expected to come into effect from 2008 - including the roll-out of the foundation phase for primary pupils, the Welsh baccalaureate, reforms of GCSE programmes, and an increased focus on key skills and progression.
Mr Williams said he understood concerns about workload, adding: "There will be work associated with implementation. But we do not expect the new arrangements to give rise to any more work than the old ones."