I have exactly 0 knowledge of the situation in California, but I'd be curious if they have (on top of my head, might be missing many more factors)
reply- adequately paid and educated teachers
- small classroom sizes
- available support for special needs kids
If all of these are in place, are the bad outcomes explainable by poorer socioeconomic factors? And are there any forced learning policies like standardized tests that promote rote memorization?
It just seems so far fetched that a teacher's union would single handedly sabotage the whole education system. Even if they push for a certain kind of teaching, it would simply not tank the whole ship, so to speak.
(I know I'm talking slightly past your points, but I'm mostly interested in the point of how much does the union actually affect the learning outcomes, all the other factors considered)