It would appear that the nature of their approach is first and foremost to ensure that any change they make is data-driven best practice for the situation at hand. In iceland, it included prohibition of purchase by minors and provision to minors by adults. More importantly, their changes created a situation where children were more likely to spend more of their time with adults who cared about them, in an active and engaged society. Curfews make me uncomfortable, but I can see that this encourages children to be in safe places overnight. Prohibition makes me uncomfortable, but it makes consumption more expensive and difficult, so child users will be less likely to become addicts. Widely available after-school classes and programs... have no downsides other than cost, which (it would seem) are clearly worth it.

Where does best practice lie? If I were to start a civilization from scratch, I think I would use this model as a strong data point when organizing how education and the laws pertaining to youth were concerned.

I have some more libertarian leanings than some of the implementations presented can accommodate, but perhaps if I were an Icelandic teen I would direct my frustrations on a hobby or class I picked up because my government mandated that I have access to it if I wanted to.