Researchers at Edinburgh University who track the Scottish School Leavers Survey suggests it became easier to gain entry to advanced courses such as the Higher National Certificate and Higher National Diploma in the late eighties and early nineties.
The proportion of advanced course entrants with three or more Highers fell from 77 per cent in 1984 to 40 per cent in 1993. There was also a slight decline in the average Highers grade to a C pass. In contrast, most degree entrants continued to average B passes at Higher - the traditional pattern.
Teresa Tinklin and David Raffe, of Edinburgh's Centre for Educational Sociology, warn: "It may require a rigorous approach to the assessment of outcomes if the Government's aim to achieve wider access, while maintaining high standards, is to be met."
But Tom Kelly, chief officer of the Association of Scottish Colleges, countered that the apparent decline in entry standards was down to two factors.
"Before 1992, it was not possible for HNC students to get a student award. After that, numbers went up," Mr Kelly said. "You would take someone for the one-year HNC but not the two-year HND."
Colleges might advise students an HNC would be within their grasp but not HND, much less a degree, without further work. Previously they had to sign up for a two-year HND.
The period under study also coincided with a significant expansion in student numbers. Mr Kelly said: "Between 1991-92 and 1993-94, numbers of full-time higher education students in colleges went up from 12,000 to 20,000. There was a sharp increase in the numbers entering the one-year HNC and in the recruitment of mature students."
He continued: "It does not mean that students' end qualifications have declined at all but it might mean the base of recruitment widened at that time."
The study also confirms the continuing existence of a class divide in post-16 education with students from middle-class backgrounds and with educated parents much more likely to continue their studies. The gap narrowed in the late eighties but remained significant in the early nineties.
Family background is strongly correlated with school attainment, the researchers reaffirm.
They state: "In 1993, for example, 48 per cent of leavers with fathers in non-manual occupations had attained three or more Highers, compared with 21 per cent of those whose fathers were in manual occupations."
Students from disadvantaged backgrounds were therefore less likely to apply to higher education and less likely to start courses they applied for. But entrants to advanced courses were recruited from a wider range of backgrounds. Leavers from less advantaged homes were more likely to opt for advanced courses than degree courses.
Students from independent schools were no more likely to enter higher education than comparable leavers from state secondaries but were more likely to opt for degree rather than sub-degree courses.
Differences across schools in rates of entry to higher education were explained by differences in qualifications and social background.
The most significant trend among leavers was the growth in participation. The proportion entering higher education doubled from 16 per cent in 1984 to 33 per cent in 1993.
Degree courses and advanced courses grew at a similar rate, with advanced courses continuing to account for more than a quarter of school-leaver entrants to higher education.
Curiously, although females left school with higher average qualifications, they were less likely to enter higher education. If they applied, they were less likely to start courses.
Scottish School Leavers Entering Higher Education is published by the Scottish Executive Education Department Research Unit.