HOW can you come to a ridiculous conclusion when every step you take seems logical? You know the sort of thing in medicine - a pill for this and a pill for that, pills for the side effects and pills because the combination has an unfortunate effect. Before you know it, the average pensioner has a handbag full of pills.

The answer is fuzzy logic. Each step may seem logical, but in fact only follows 80 per cent logically. This is enough for one and maybe two steps but rapidly approaches little better than guesswork a short distance down the chain.

This is what has happened to assessment in schools. The mushroom-like growth of investigations, portfolios, tests of practical ability and so on has led to the ridiculous situation where about a quarter of all the time supposedly for curriculum development in schools is actually used feeding the ravenous beast that is assessment.

Step by seemingly logical step, the structure of internal assessment has grown, with careers hitched to the bandwagon of ever more varied and time-consuming assessment instruments. Luxuriant growth followed by slashing back characterised Standard grade internal assessment. But like a pruned rose, the flower burst forth even more strongly in the form of Higher Still.

It is possible to gain an honours degree from a Scottish university on the strength of five three-hour exams, but that is not good enough for the Scottish Qualifications Authority. To achieve five Highers, it is now necessary to pass five external exams (often shorter than three hours, to be fair) and three or more internal unit assessments, often made up partly of written tests and partly of other requirements, together with all the extra requirements dreamt up by Higher Still development officers. The quantity of formal assessment is greater, often considerably greater, than at university level.

It was all very well the Education Minister calling, in 1998, for teachers to spend less time on bureaucracy, while at the same time his department, guided by HMI, was putting the final touches to a massive increase in administration in the form of Higher Still.

Who was the minister? Brian Wilson. Was it his fault? Probably not, since he barely had his feet under the table before he was moved on. It was really Michael Forsyth and the inspectorate, his Praetorian Guard, who set this juggernaut in motion.

Politically, there is a big error here. The people who will pay for this will be the local authorities. But they have not yet seen the itemised bill. The SQA is still under the shelter of Jack McConnell’s financial umbrella, erected to keep the sky from falling on him the way it fell on Sam Galbraith. We can expect, and indeed demand, some very pointed questions when cash-strapped councillors realise what is going on: Higher Still and Standard grade cost twice as much as a perfectly adequate and more workable system.

They also take up an average of 40 hours a year of precious teacher time (more for English teachers, of course, despite the changes). The commitment to a 35-hour week was seen by directors of education as opening the door to real curriculum development by making available around 160 hours per teacher. Instead the time-auditing process introduced for the first time this school year has shown the real cost of SQA assessment in teacher time, and it is untenable in the long term.

The situation will become worse once the SQA and HMI get round to enforcing the cumbersome internal moderation procedures. There is considerable anecdotal evidence that these have not been adequately time costed by school McCrone committees, and will appear as a major item as soon as the requirement for internal moderation starts to be enforced.

The recent, rather biased, consultation on internal assessment closed last month. The National Qualifications steering group will have to sort out the mess that is Higher Still. It will either wield a big axe, or condemn Scottish education to slide into a morass of tedious, expensive and wholly unnecessary internal assessment. Only a boycott by those who see most clearly what is happening - the teachers - can rescue the system if the steering group fails to grasp the nettle now.

Graham Dane teaches in Edinburgh and is a member of the executive council of the Educational Institute of Scotland. He writes here in a personal capacity.