If unions were the cause of "mediocrity" then there should be better teaching in states that don't have teacher unions right? Ranking of states without unions

If unions were the cause of "mediocrity" then there should be better teaching in states that don't have teacher unions right? Ranking of states without unions (2011) https://www.businessinsider.com/states-where-teachers-unions-are-illegal-2011-2 https://www.businessinsider.com/states-where-teachers-unions... Wisconsin after unions were removed (2017) https://money.cnn.com/2017/11/17/news/economy/wisconsin-act-10-teachers/index.html https://money.cnn.com/2017/11/17/news/economy/wisconsin-act-...