Teachers Unions

With the caveat that correlation does not necessarily denote causation, check out this chart showing states' political leanings, strength of teacher unions, and adoption of literacy policy principles.

Mulling the inverse relationship between literacy score and teacher union strength, it seems clear that teacher unions are opposed to the adoption of good learning practices! Where unions are strong, few such practices have been accepted. 

Reflecting on this data, the website Issues & Insights concludes thusly about teacher unions.

Add it all up, and you have organizations that extort money from taxpayers to finance a protection racket for themselves, their Democratic patrons, and various far-left causes (which few taxpayers would support), while engaging in fraud by pretending to be looking out for the interests of public-school students.

Harsh, but mostly true.