Roger McClure, chief executive of the Scottish Further Education Funding Council, said colleges were doing consistently well. "We should all be proud of this remarkable national resource," Mr McClure said.
Of 3,728 "episodes of learning" observed during subject reviews over the three years, 90 per cent were classed as very good or good and only 10 per cent as fair.
Inspections of college-wide aspects, which cover areas such as leadership, curricular support, access and quality assurance, showed that almost all grades for staff were very good or good. The lowest score for college activities, at 80 per cent, was for quality improvement.
Inspectors urge colleges to pay more attention to weaknesses in teaching, including a narrow range of teaching and learning approaches featuring "excessively didactic structures (which) reduced learner interest and motivation". Also criticised were "minimalist" approaches which followed too closely the demands of assessment.
These factors inhibited student achievement and led to substantial numbers dropping out of many programmes.