The finding came as the Scotland Against Drugs campaign was launched in Aberdeen on Tuesday. The initiative was immediately criticised as misguided and counterproductive by some drugs agencies, despite the backing of the four main political parties and the churches.
But the council's survey does not bring entirely bad news. Thirty-nine per cent of leavers say their attitudes to drugs were influenced, while 64 per cent report an increase in knowledge. Only 14 per cent say health education had no impact.
The researchers add that young people will continue to experiment. One youth said: "You have to try for yourself because you never believe unless you try for yourself."
A similar tale emerges over drinking. Ninety-four per cent of leavers say health education programmes have no effect. Behaviour, attitudes and knowledge about HIV and sex education do, however, appear to be influenced by teaching programmes.
The researchers conclude that health education appears to be more successful in giving school-leavers the facts about drugs, smoking, HIVAids and sex education than in changing their thinking or behaviour.
Forty-three per cent say HIV education has influenced their behaviour, 61 per cent their attitudes and 64 per cent their knowledge about the virus and its link with Aids. One in three say their sexual habits have been influenced by programmes, while 46 per cent admit to changed attitudes. Sixty per cent say they now know more about sex.
At least half felt they were more informed about drugs, Aids, sex education, alcohol and diet. "Considering that the first four of these are the areas identified as priorities these results are encouraging," Marion Devine and Jacqueline Mapp, the researchers, say.
Ms Devine concludes that the success of health education programmes depends on the relationship between pupils and teachers. She comments: "Health education covers some of the most sensitive and controversial matters likely to be raised in school. Pupils need to feel a sense that they matter as individuals in all their contacts within the school.
"A school which sets a high priority on relationships and consideration for others at all levels is likely to be more effective than one in which health education is a matter for guidance and social education staff only."