Therein lies the problem: addiction does not readily yield to teaching not to abuse the drug. In the US there has been an intensive 50 year campaign to educate people not to use tobacco, yet nicotine dependence remains a top public health problem.
Addiction research has shown compulsive drug use is associated with actual alterations in brain structure and functional circuitry. Treating addictions has proven to be a notoriously difficult problem to solve, meaning prevention is a far higher priority than attempting to cure.
I believe the scientists studying the matter would disagree that rate of drug abuse would decrease solely on the basis of education, especially among the subset of the population that is most vulnerable to developing compulsive use in the first place.
Trouble is, drug response, including bad effects, is probabilistic. Exposing large populations to a drug with predictable harmful effects in a substantial subset, it's really a crap shoot who will wind up in trouble. Minimizing initial exposure to the drug may be a reasonable preventative strategy.
But don't take my word for any of it. Check out the scientific info sources for yourself, see: http://www.drugabuse.gov/
The states permitting wider use of cannabis admit it's a kind of experiment, a bet on the hypothesis that the harmful effects of it (abuse/dependence, MVAs, health problems, more child/adolescent use) will be offset by decreased burdens imposed by criminal justice systems. The jury's out on the question, we'll have to wait a few years before the verdict is in.