There are differing schools of thought on the mental health aspect of cannabis use, the propaganda coming from the government claims that stronger strains being bred these days are leading to higher instances of mental health problems. Currently the strongest strain of cannabis weighs in at around 25-30% THC but when you take into account that in the sixties the hashish being smoked was up to 90-99% THC due to the process of shaking the crystals from the bud to press into hash then the propaganda does not hold water.
Remembering the same people who are making the purity claims are the ones who are claiming the links to mental health then they become a little less credible in comparison to the experts on the other side of the arguement who claim that the increased link between cannabis and mental health is due to people self medicating and cannabis use is in their view a symptom of mental ill health rather than a cause. In all honesty there is not enough research into the subject to make any solid claims either way.
As for the substances of "doubtful quality" then one way around having our kids smoking hashish adulterated with boot polish, excrement, plastic, straw, urine, or in the case of herbal cannabis (grass) plastic or glass beads sprayed on with a "glue" to look like THC crystals which have previously been shaken off is to legalise the stuff, then users could grow their own and be totally assured of the quality, the government could also set down standards which those who do not wish to grow their own could have a level of assurance of the product they receive.
I have to say that your stance surprises me John given that you had a marijuana leaf as an avatar once and your signature used to say "pass over my pipe, I'll have a wee puff"
You talk a lot of sense mate but I'm afraid your a long way off the mark if you think the hashish in the sixties was over 90% THC .