Well I appreciate you letting me know that.
Combined SAT/ACT rankings for the states without collective bargaining rights for teachers:
* South Carolina -- 50th
* North Carolina -- 49th
* Georgia -- 48th
* Texas -- 47th
* Virginia -- 44th
Wisconsin ranked second, according to the source cited by the Economist.
Source is here: Unions: Teaching quality and bargaining | The Economist
A more lucrative contract means that the schools have a greater number of applicants to choose from when filling the position. The converse of this is that districts offering shit-contracts (sup Texas) get fewer applicants, and less qualified teachers.
QED
Did you know Washington D.C. spends the most per pupil in the country, yet has pretty much the worst test scores in the industrialized world?