1) 'Jail' - I never said they should jail them. But they should jail the dealers, yes. Moreover, 'required rehab' would be beneficial.
In Canada (a prison in Ottawa, specifically) if you 'go in' an opioid addict, the actually give you 3 doses of methodone a day. A friend of mine in there for a few days (small thing) described them as insane zombies, banging on the door to the clinic when it was almost time for their next dose.
The 'short term' harm reduction ideal of 'giving them drugs' might be nice, but in the 'long term' - keeping people jacked on opioids for months at a time has to be one of the most cruel things imaginable.
2) I think that most 'high schoolers' grasp that heroin, meth and coke are far worse than weed.
3) This is a separate issue. In other countries, such as Canada, we still have 'the war on drugs' - and 'free healthcare'.