Conservative policies widened educational inequality despite an overall improvement in attainment levels, research into the Scottish Young People's Survey has found.
Pupils from working-class homes are achieving better results but falling further behind their peers, more of whom are going on to further and higher education.
Paula Surridge, a sociology lecturer at Aberdeen University, said examination of the leavers' survey between 1985 and 1993 showed the persistence of social class in determining post-school destinations. Father's occupation and mother's education are the two crucial indicators. "The son of a bricklayer is now further behind the son of a bank manager than he would have been 10 years ago," Ms Surridge told The TES Scotland.
"These findings are particularly striking as they show that, even after the decision to stay on at school and the effect of qualifications are taken into account, social class differences in educational performance still exist. "
She argues that the challenge is to explain inequalities "rather than to assume that increasing levels of education will alleviate them".
Ms Surridge concludes in her paper, Changing pathways: participation in post-16 education in Scotland, 1985-1993, that young people from lower social backgrounds do less well in Standard grade exams than those from higher social classes. The trend is increasing.
The mother's education has a greater impact on attainment than the father's and those with unemployed fathers do less well. Living with a lone parent has no significant impact on how well young people do. Attainment in S4 is the largest single influence on staying on, followed closely by truancy.
Ms Surridge found the strongest predictors of unemployment at the age of 19 are being without work at 16 and having no qualifications at the end of S4. "This model is suggestive of a group of young people at the bottom of the heap with no qualifications and few prospects."