The teachers’ strike was barely over when a Tribune editorial hit the streets ripping unionized schools and lauding nonunion charters, starting with one run by UNO, a Mayor Emanuel favorite.

“The good teachers know they’ll do fine. They’ve got the confidence. I’ve talked to them. I know,” Rauner said, according to a story by the Trib‘s Rick Pearson. “It’s the weak teachers. It’s the lousy, ineffective, lazy teachers that—unfortunately, there are a number of those—they’re the ones that the union is protecting.”

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A common theme runs through these messages, and it’s based on a myth that goes like this: charters far outperform unionized schools because countless “weak” teachers keep their jobs thanks to union contracts that protect tenure. No matter that tenure no longer exists in the Chicago Public Schools, or that factors like poverty and crime and parental involvement may play some role.

Look, charterheads, I get it. You hate the teachers’ union, if only because it funds rival political campaigns.

There are 541 elementary schools in Chicago. Based on the composite ISAT scores for 2011—the last full set available—none of the top ten are charters. None of the top 20, 30, or 40 either.

I don’t mean to pick on them. Well, maybe a little. All right, a lot. But c’mon—you have to admit Rangel brings it on himself by almost gleefully allowing his students and schools to be used to bash the teachers’ union.

This advantage was a central point in a recent New York Times article in which one north side parent said she’d enrolled her son in a charter because he wasn’t being “challenged” in the local neighborhood school, where teachers had to spend “too much time disciplining troubled students.”