It is definitely a responsibility of the tzibur to ensure that rabbeim get a living wage.
Rabbeim don't get a living wage, but by the same token, their job doesn't utilize their full working potential. Working men can put in far more hours and far more days into earning a living than that. And if that was how schools were organized, the money used to pay other people could augment rabbeim's salaries and get them employee benefits.
Ever heard of a school downsizing?