There is no such thing as a perfect test. But it is still necessary to see how children are doing and to monitor standards.
In Wales, they have come up with some radical ideas for assessing 10 and 11-year-olds. They started by putting children's learning at the centre of thinking.
From there, Professor Richard Daugherty, dean at the university of Wales, Aberystwyth, and his independent committee, came up with the idea of learning skills tests, sat at the end of Year 5, which would be "directed towards a clear educational purpose, that of supporting the learner's transition from primary to secondary school".
Their interim report also called for an end to Sats in Y6, with well-moderated teacher assessment instead.
It was pointless and costly to have two types of assessment doing the same thing, especially at a time when virtually no use is made of the results to benefit the pupils themselves. But a good system of moderated assessment can help teachers' own learning.
Skills tests in Y5, in literacy, numeracy and "enquiry" across the curriculum, would not only free up Y6 for exciting activities but would indicate where individuals need help before moving up to secondary school.
"It is a new animal," says Professor Daugherty. "The committee asked itself, 'If we want to know about learning, what is it that we want to measure?'" So far, ideas are far from well-developed and creating, testing and ensuring the reliability of this new beast is a job not to be underestimated - not to mention all the angst as teachers are trained in and struggle to use the new system. Nevertheless, Professor Daugherty believes it will be all worth it.
If the Welsh Assembly approves the idea after the final report comes out in the spring, the Welsh curriculum council, ACCAC, will have to build up a developmental scale for each set of learning skills.
Professor Daugherty says such tests need to be statutory to bring consistency. At present most schools use a range of commercial cognitive abilities tests (often based on puzzle-solving) to help identify children's strengths.
"After initial discussions within the group, we concluded that lack of clarity about the purposes of national curriculum assessments was making it difficult to evaluate the current statutory arrangements," says the report.
"A clear definition of the potential purposes of assessing pupils' attainments is essential."
And there was no doubt about the central purpose. "Learning was at the heart," says Professor Daugherty.