There are also fears, The TES Scotland understands, that the tests may not be ready and could place undue strain on the Scottish Qualifications Authority, which will administer the system.
The New National Assessments, as the tests are dubbed, were first signalled 18 months ago by Jack McConnell, the then education minister, following a year-long consultation on 5-14 assessment.
Mr McConnell promised to integrate current tests, which confirm the levels pupils have reached, with the Assessment of Achievement Programme sample tests to allow more rigorous monitoring.
A Scottish Executive spokesman said this week it was "still on track" to replace the current tests with the new national assessments. Full details of what ministers are certain to trumpet as a significant revamp are likely to emerge later this month, ahead of the May elections.
It was suggested in autumn 2001 that AAP tests, which presently sample 5 per cent of the cohort in English, maths and science, would be used to validate the results of the revised 5-14 tests. Studies in several authorities have shown significant disparities against standardised tests.
Pupils can be working at the wrong curriculum level, and are sometimes two levels below their capabilities.
Meanwhile, the authoritative AAP exercise is expanding to modern studies and modern languages, giving it more clout in secondaries.
At the same time as clearing out the present batch of 5-14 tests, the Executive is developing a longer-term strategy on assessment and reporting which is being piloted in around 170 schools.
A particular worry for the Educational Institute of Scotland is the workload implication of personal learning plans for all pupils.