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.

"Fuentes isn't a traditional Chicago public school, but part of the United Neighborhood Organization network of charter schools, run under different rules without union teachers," the editorial reads.

Students there "outperform students in traditional Chicago public schools."

That September 19 assault came a day after Bruce Rauner, a mayoral ally and charter funder, declared war on unionized teachers in a speech sponsored by the Illinois Policy Institute and the President George W. Bush Institute, which I'm sure retains all of the former president's conservative compassion for the low-income kids of Chicago.

"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."

By the end of the week Mayor Emanuel himself had rushed off to make sure everyone saw him show up at the opening of UNO's new Galewood campus—its 13th and counting. Just in case anyone wondered where his allegiances lay.

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.

Therefore, we must annihilate the teachers' union so the "weak" teachers can be replaced with the untold thousands of "good" ones eager to teach in charter schools where they can work longer for less—at the whims of autocrats who can fire them for not doing what can't be done. Like UNO CEO Juan Rangel did to David Corral, a former gym teacher fired for not being in two places at once.

As if any teacher—good, bad, or mediocre—would want to come to Chicago for this.

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

But if you want to fight the union, at least use the facts. And the central fact is this: the nonunion charters are not outperforming the unionized schools. No, it's just the other way around.

I get no delight in reporting this. OK, maybe a little. But I have a soft spot in my heart for charter school teachers, especially those who work for lunatic bosses. I presume most of them are in for all the right reasons, like their desire to teach kids. But I'm also guessing that many would want to join a union or at least get the protection offered by a union-negotiated contract, just in case they accidentally look cross-eyed at their principal when he's having a bad day.

Besides, the chief barometers for measuring good versus bad are standardized tests that bear little relation to anything of value that anyone would eventually do in a real profession, or in life. Plus, students can improve their scores by taking special classes, should their parents be able to afford them. Which is another way of saying that higher scores can be bought—like just about everything else in Chicago.

But as I was saying, the foes of the teachers' union declare that we should pay close attention to the all-important standardized test scores. So let's take a look.

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.

In fact, you've got to go to 41 to find a charter. Take a bow, CICS Irving Park!

Most of the 49 charters on the list are clustered near the great middle, alongside most of their unionized neighborhood schools.

The top scorers are public schools with unionized teachers who are members of the Chicago Teachers Union. That's the one whose president, Karen Lewis, somehow brainwashed her easily duped members into thinking they wouldn't rather work at a charter school.