> But do we live in an age where parental and community authority are so diminished that parents need the power of the state to bolster their discipline of their kids?
It's not that dramatic; it's just that at school the parents are absent, and the teachers' authority is typically undermined by the parents --
congratulations if you are not one of them, but in such case I am simply talking about your kid's classmates' parents.
Try to limit the children's freedom in any way (e.g. take away their smartphones if they play Angry Birds or browse Facebook during the lessons), and at least one of the parents will complain and threaten to sue the school. The easy way out for school administration is to let kids do whatever they want to, and formally require teachers to maintain discipline in the classroom while simultaneously forbidding them to do anything that could actually have an impact.
The best strategy for a parent is to try finding a school when parents of other children are not idiots. That is typically easier said than done. What I would recommend is trying to find something unusual -- for example I would choose Montessori education for my kids; not because I think it is a superior option per se, but simply because it is not the default option, and I expect the most stupid parents to go for the default option, so this is how I would try avoiding them. Problem is, if this strategy becomes too popular, many of the idiots will choose it too, simply because they heard somewhere it was the right thing to do. (It's complicated because some of the idiots also want to get the best education for their kids; they just can't stop themselves from trying to undermine it the moment someone provides negative feedback to their kid.)