Teachers' judgments should drive assessment as the new curriculum develops, according to a Glasgow University expert on assessment.
But that will only be achieved if there is a greater focus on teachers' capacity to share standards in their own schools and with others, warned Louise Hayward, co-director of the university's research and knowledge transfer group on teaching.
Education Secretary Fiona Hyslop is due to announce in the next few weeks the Government's thinking on how A Curriculum for Excellence is to be assessed.
Speaking last week at a national seminar on assessment, Mrs Hayward outlined some of the findings in Assessment in Schools: Fit for Purpose?, the latest report produced by the Teaching and Learning Research Programme, which makes the case for a rethink on how learning is measured and what areas of learning are assessed.
She insisted that assessment for learning must remain a Scottish Government priority at all levels in the system, including the final years of secondary - a time when teaching has tended to be dominated by exam preparation and rehearsing exam questions.
"We need to develop ways of assessing young people externally that are not so predictable as the current examinations system," Mrs Hayward told The TESS.
Currently, teachers tended to try and second-guess what exam papers would contain by looking at past papers and rehearsing with pupils the questions that come up year after year.
The S5-6 stages were very assessment-focused and the whole curriculum became "a series of rehearsals for the exam", she said. That, however, did not necessarily measure pupils' wider or deeper learning.
"When designing the new qualifications, we need to design them in ways which make them less susceptible to pretty arid rehearsals," she added.
Mrs Hayward warned, however, that whatever changes were made, they must not put young people at risk. "The stakes are high. These are the examinations that either open doors to young people or close doors, so it is really important to think all of this through very carefully.
"I think teachers would have to be part of the process of thinking through what the new system would look like. If you talk to teachers, they are often very dissatisfied with the kinds of experiences that young people have in the later stages of secondary school, so teachers do realise there is a problem."
The really rigorous information about pupils' learning should come from teachers' everyday interactions with them, she said. Wales was only one of a number of countries working on a national assessment system of this kind.
England, on the other hand, which spends #163;750 million a year on direct and indirect testing, had placed a very heavy reliance on national testing. However, as England did not have a sampling system like the Scottish Survey of Achievement, which acted as a cross-check, it was not possible to say if better learning was actually taking place, Mrs Hayward suggested.
Innovative work based on formative assessment in the Highland Future Learning and Teaching (FlaT) programme, led by Kevin Logan, has already shown how successful new approaches to assessment could be, Louise Hayward says.
Senior pupils have done better than expected - increasing their grades or recording a lower drop-out rate - after being exposed to formative assessment approaches, she notes.
"What we need to do now is work through ways of making this happen right across the country," she said.
The central problem with the current system was that "assessment information has become a proxy measure to facilitate judgments on the quality of most elements of our education system: its teachers, headteachers, schools, support services, local authorities and even the Government itself", she argued.
"This represents a fundamental change from the situation even 20 years ago, when test and examination results were predominantly meant to serve as indicators of what a pupil knew and understood of a subject."