From all the wailing about mayoral control and reform money pouring into the state you might think that unions were weak in Illinois. But that's not the case at all according to this new rating of state union strengths, described by its authors (DFER and Fordham) as "the most comprehensive analysis of American teacher unions’ strength ever conducted." Still, the strength of Illinois unions is not uniform from one category to the next.Over all, Illinois comes in 8th nationally (PDF) according to the report -- among the top tier over all in terms of resources, influence, legislation, etc.
But this result comes from a wide range of factors, not all of them uniformly strong. It's ranked #3 in terms of influence over the scope of bargaining, for example -- dues are automatic, strikes are permitted -- but #12 in terms of political involvement, #18 for resources, #28 for perceived influence, and #39 for state policies -- there's tenure after four years, class size is restricted in the early grades, etc.