May I correct your typo to show that I'm not totally ignorant? ;-)
The public school system may be terrible, but for most families, it's the only one available. Fortunately or unfortunately, the quality of a particular school is largely a function of the condition of the community in which the school exists.
You may feel I'm "propping up" the system, I feel I'm working to change it from the inside. As long as most educators are liberals, the system will never change, or will only change cosmetically.
I don't belong to the union, because I refuse to support them. Please understand that not belonging to the union carries risks, because union membership is the only method of purchasing professional liability insurance in my state, and teachers can be sued personally as well as professionally.
The bottom line, however, is that it's not just the teachers, and it's not just the system: it's also the families, the communities, and the culture. Schools won't change until and unless all of these change.