This is not so much because the picture is uniformly bleak - the Office for Standards in Education found many examples of good work from students and laudable attempts to improve the notoriously bureaucratic marking process - but because they uncovered worryingly wide variations in the quality of work, confusion among teachers about the criteria for grading it and inadequate arrangements for checking the consistency of marking.
Commenting on the report yesterday, the chief inspector, Chris Woodhead, said it was crucial that employers, students and teachers were confident about standards in vocational education if it is to acquire equal status with academic qualifications.
"This report clearly shows that there is some way to go before that confidence is justified," he said.
The report, based on visits by the inspectorate to 60 sixth-forms in autumn 1995 and spring 1996, found that teachers in 20 per cent of schools were confused about how much work students needed to produce to achieve a pass in each vocational unit. A quarter of schools also demonstrated weaknesses in the "regularity and accuracy of assessment".
The inspectors describe how one intermediate business course student had obtained a diagram of a local firm's organisational structure and included it in his folder, without indicating that he understood it. He was given a pass. Another group of business students submitted "neatly written copies of their questions and answers" after a visit to local companies, with no written demonstration that they appreciated the underlying commercial issues.
The OFSTED report on GNVQ assessment follows and largely reinforces the message of another report, by Dr John Capey, last November. It will give a clear focus for the way in which the Pounds 10 million, earmarked in April by the Department for Education and Employment for the revamp of GNVQs, is spent.
The National Advisory Council for Vocational Qualifications's chief executive, John Hillier, said that he was aware of the problems highlighted by Ofsted, "but they tend to be confined to small schools in remote areas. The important thing to remember is that 6,000 GNVQ advanced level candidates got into university last year".
Tim Oates, research director at the council, said that "GNVQs are on the brink of becoming a mature qualification. I would be extremely disappointed if we see the same problems after we implement the recommendations of the Capey review. The OFSTED report is helpful in clarifying what needs to be done."
He said that training for GNVQ teachers had been revised and work was under way to trim the bureaucracy from assessment and make the checking of marks more precise.
Inspectors found a general lack of rigour in the assessment of core skills because teachers were reluctant to fail students on a particular core skill if this might lead to them failing the whole award. In communication, teachers did not have a clear understanding of the standards required at each of the three levels and did not correct language errors in written work.
In information technology, many teachers were insufficiently experienced to judge whether requirements at the three levels had been met.
While the assessment of work against the grading criteria has improved, teachers in almost half the schools visited did not fully understand how to interpret and apply all the criteria and some gave work a higher grade than it was worth.
The assessment burden on teachers was found to be excessively time-consuming and bureaucratic: "Experienced GNVQ teachers report that the whole process can take up to 18 hours for one assignment for a group of 12 students."
Of the thousand "external verifiers" - people employed by the three GNVQ awarding bodies to check the quality of assessment - only half were specialists in the relevant vocational area. OFSTED is highly critical of the verification process, which it says emphasises checking coverage rather than standards of achievement, while the samples of students' work were unacceptably small and "did not provide secure checks against copying and plagiarism".
Two of the awarding bodies, City and Guilds and the Royal Society of Arts, do not require their verifiers to talk to the students about their work and whether they understand the standards expected. Schools lacked confidence in the verifiers' methods and, says the report, there was little evidence of verifiers checking core skills because most had no experience in this area.
In one case, say the inspectors, grades on an intermediate leisure and tourism course were raised from pass to merit for all seven students, "when in the inspectorate's judgment this was not merited".
Teachers the inspectors talked to were harshly critical of the training courses available for teaching and assessing GNVQs - until recently run by the Training and Development Lead Body.
The Department for Education said "vigorous action" was being taken to address all the issues for attention in the report.