There you have it - teachers' unions are a political cudgel used for resource hoarding among the most senior teachers and affluent districts, with no attendant benefit to students or teaching productivity.
I found a few interesting articles down another rabbit hole discussing lower pay and the link to factors (which appear to be strongly correlated to the presence of collective bargaining) lowering teacher quality over time. IOW, unionization drives away high quality teachers, and may be contributing to a lower average quality in the teacher talent pool over time...will definitely be digging into this bit of the literature with interest!
