The research, conducted by researchers at the University of Washington and University of Melbourne, compared drug policies in schools in Washington state, in the US and Victoria, Australia to determine how they affected student marijuana use.
Pupils attending schools with suspension policies for illicit drugs were found to be 1.6 times more likely to use the drug over the next year than peers at schools without such policies.
Co-author of the study Richard Catalano, professor of social work at the University of Washington, said that he found it “surprising” that “suspensions are certainly not having a deterrent effect.”
In contrast, the report found that students attending schools that have a policy of referring users to a school counsellor were almost 50 per cent less likely to use marijuana.
Other methods of responding to drug use including sending pupils to educational programmes, expelling them or calling the police were found to have no significant impact.
Data for the research, published in the American Journal of Public Health, has been gathered since 2002 and surveyed more than 3,200 seventh and ninth-grade (Years 8 and 10).
Washington and Victoria were apparently selected because they are similar in size and demographic but differ considerably in their approach to drug use among students.
Washington schools are more likely to suspend students or call the police whilst Victoria schools emphasize a harm-reduction approach that favours counselling.
The study further found that marijuana use was higher among Washington students than those in Victoria. Almost 12 per cent of Washington ninth-graders had used marijuana in the last month compared with only 9 per cent in Victoria.
Cannabis has been legal in Washington state since 2012 but only permits use over the age of 21 whilst it is illegal in Victoria.
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