The study, conducted with researchers from the University of Washington, compared drug policies and their enforcement at schools in Washington state and Victoria, Australia.
Students attending schools with suspension policies for illicit drug use were found to be 1.6 times more likely to use marijuana within a year than students at schools without suspension policies.
“That was surprising to us,” said lead author Dr Tracy Evans-Whipp from the Murdoch Childrens Research Institute. “It means that suspensions are certainly not having a deterrent effect. It’s just the opposite.”
Counselling and abstinence-based drug policies seemed to work better.
“Students in schools with a policy of sending policy violators to a teacher for counselling on the dangers of marijuana were almost 50% less likely to use marijuana,” said Evans-Whipp.
The data is published in the American Journal of Public Health.