One in five colleges would be in special measures if they were schools, David Bell, chief inspector, said this week.
The head of the Office for Standards in Education voiced his concerns as he prepared to publish the first annual report to include the performance of colleges.
Inadequate management of teaching and learning is the biggest cause of under-achievement found by the inspectors in more than 100 colleges in 20012 - the year Ofsted took over inspection of 16 to 19-year-olds in colleges.
In almost a quarter of colleges inspected, leadership and management were unsatisfactory. Attendance at classes - 85 per cent in sixth-form colleges and 76 per cent in general FE - was too low and the most vulnerable pupils needed to be better served.
However, while expressing his concerns, he acknowledged that causes of failure rested partly with an education system that since 1993 expected too much of colleges beyond the immediate pressures to improve teaching and learning.
In response to the findings in Mr Bell's report, college leaders say they welcome the fact that Ofsted "sets an agenda" for improvement. But they challenge some of the "stark" conclusions drawn. The Association of Colleges said it had "concerns about how well the inspection process measures learning in colleges".
The Ofsted report says: "Most teaching of post-16 students is at least satisfactory and a great deal is good. But the teaching in FE colleges is more variable and there is too much unsatisfactory teaching."
The chief inspector's central criticism is the paucity of choice for lower-attaining students. "Higher-attaining pupils almost always have at least a satisfactory choice of courses, but lower attainers at 16 often have inadequate access to education and training opportunities suited to their needs."
Mr Bell says the lack of choice and coherence of what was on offer for students at levels 1 and 2 (GCSE-equivalent) fosters disaffection.
However, Judith Norrington, AoC director of curriculum and quality, said:
"The dilemma is that we are being told to widen participation and reach the unreached. But these students aren't used to coming to any education establishment and are a risky commodity.
"That is not to say we should be offering poorer quality, but for some students, coming through the door is an achievement."
David Gibson, chief executive of the AoC, said Ofsted should look again at how performance of teachers and curriculum managers is measured and whether it can fairly be compared with school achievements. "It is important to remember that judgments on leadership and management are built up from a view of subject areas."
"These are examined in up to 14 blocks. If two blocks are considered less than satisfactory, this can lead to a college being judged as failing. Most provision in what is labelled a failing college can therefore be satisfactory or better."
Mr Bell said the telling comparisons were between general FE and sixth-form colleges. "The good-to-excellent provision in sixth-form colleges is 38 per cent, compared with 28 per cent in general FE."
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