CHICAGO – This week, the Chicago Teachers Union approved a resolution against national Common Core curriculum and testing mandates, soon after Oregon’s teachers union made similar moves and four months after the same from New York’s.

How helpful of them to throw their political weight against the mandates now that it’s unlikely they’ll be fully repealed in more than a few states. And of course the union’s vote is based on principle rather than the fact that new tests coming down the pike may hurt unions by bouncing low-performing teachers onto probation and revealing that public schools aren’t educating as well as many think.

It’s difficult to cut this Gordian knot because union protections for bad teachers should be repealed, but states’ new test-tied teacher evaluation systems are ham-handed, biased central planning dictates. So is Common Core. Cartels and monopolies are never a good idea, whether the particulars emanate from unions, state legislatures, or the Obama administration. So while teachers unions are almost certainly not motivated by what’s best for kids (because they’re actually about preserving jobs for their members instead), they’ve got a point.

MORE NEWS: Know These Before Moving From Cyprus To The UK

Even a broken clock is right twice a day.

Aside from snark, what may this portend? First, it makes quite clear what folks said long before Common Core passed based on the audacity of its aspirations rather than evidence of likely accomplishment: “Implementation” will grind it into nothing. Central Planning 101: It’s impossible to micro-manage so many people. In other words, bigger unions starting to take the hint from their locals indicates that, despite all the push-polling showing otherwise, most teachers are not likely to make sweeping changes to their practice just because some shiny-faced bureaucrats somewhere have a big idea. In fact, they rather resent yet another intrusion.

Second, this complicates the already-insane Common Core politics, for until now the most visible and effective Common Core opponents have been Tea Partiers, who are hardly union-friendly. So this makes the weird underground alliances among right and left against Common Core even harder for sound-bite politicians to digest. Certainly it’s not as easy as “the enemy of my enemy is my friend” adage.

But here’s another, more useful proverb: If everyone can smell it, it definitely stinks.

Authored by Joy Pullmann