The latest exclusion figures show there were 57 cases per 1,000 pupils last session, a drop of just over 11 per cent.
The total stands at 39,717 but, as some pupils are excluded more than once, the actual number of individuals shown the school door last year was 20,600, which represents 3 per cent of pupils.
Maureen Watt, the Schools Minister, said that "the significant drop in exclusions is a clear indication that the range of approaches and provision available within and beyond school is working".
She publicised the figures by visiting Inshes Primary in Inverness, which uses a "solution-oriented approach" to tackling the underlying causes of indiscipline, the result of which has been that there have been no exclusions at the school since it opened 18 months ago.
But Ronnie Smith, general secretary of the Educational Institute of Scotland, said: "We need some explanation for such a dramatic reduction. I would have expected the figure to have plateaued after some years where there has been an increase following the Government's decision to remove exclusion targets. Many teachers would raise an eyebrow at these figures.
"We should be cautious about treating the figures as a proxy for the scale of indiscipline in schools. It's a rough guide, but the attitudes of individual headteachers and local authority policies do influence the position."
Jim Doherty, acting general secretary of the Scottish Secondary Teachers' Association, suggested that the drop in exclusions could be a result of pressure on schools by local authorities to drive the numbers down.
But Mr Smith said that, if this was so, he would have expected the relative position of authorities to change. Yet the "top and bottom excluders" remain largely the same. Most exclusions occur in Dundee where the rate is 112 per 1,000 pupils, followed by Glasgow (97) and North Ayrshire (92). The fewest are in East Renfrewshire and Orkney (10 per 1,000 pupils), followed by Shetland (14) and Stirling (30).
These figures suggest the same factors which affect exam results are at work: exclusions are more likely to involve boys, pupils in upper primary and lower secondary, those in deprived areas, youngsters with special needs and children in care.
The 11 per cent drop also disguises increases in particular categories: exclusions for assaults with a weapon have risen by 28 per cent and substance misuse by 26 per cent.