It breaks my heart to hear from an (older) friend who's a substitute teacher, a bright woman who's a good person with a number of skills, that she's having enormous difficulty making ends meet on her sub-20k salary. For such a necessary, important job to be matched with a barely livable salary is tragic. If I were living in outer suburbs, I probably wouldn't even know her - people who know people who work such jobs or who can really appreciate their importance would find it hard, I think, to justify such financial arrangements to themselves.
I'm sure some people would suggest she get a better job - that's broken thinking on two counts - she doesn't have the right degrees to get a better teaching job (and getting them isn't financially/jobwise feasable), and the job needs to be done (and should ideally be done by an intelligent, good person) regardless of if she's the one doing it. A society that does not take efforts to keep itself working, whatever the larger economic model, is a society destined for ruin. I regret that both her and the children are failed by the system.