School definitely will open as scheduled Sept. 6. Hundreds of thousands of kids will head out the door and return that afternoon, hopefully a little more educated. But after the first week of October or so—optimal time for hitting the picket line—all bets are off.

CTU President Karen Lewis and especially her membership need to grow up and realize this is not the time to try to break the bank, or Mayor Rahm Emanuel. He just moved, after all, to hike taxes by $1.1 billion for the benefit of teachers and other employees and retirees of Chicago government.

But if Lewis' task is to lead a union that doesn't want to be led, Emanuel has an equally big challenge. He needs to stand firm and, if necessary, take political punishment in a strike, rather than spending money CPS doesn't have. The school system's finances are too close to breaking to fall into the usual pattern of saying yes and hauling out the plastic.

Given the mess CPS has been in, the mayor and his schools team actually have done a pretty good job. Not perfect, mind you. I'm mystified that a system that has been flirting with insolvency plans to spend an extra $233 million this year on school construction.

Still, test scores are improving, as are attendance rates. The system won permission in Springfield to raise local property taxes $250 million for teacher pensions, and it's been provisionally promised another $215 million in the upcoming year, also for pensions. That's better than I thought they'd do.

Though Lewis disagrees with me—”Emanuel is weaker now, “ she says—I think those realities put Emanuel in a better position to say no than he was four years ago, when CTU was threatening to take out its frustration on Emanuel's old boss Barack Obama, then a candidate for re-election.

Emanuel can look the people of Chicago in the eye and say, “Hey, you're putting in an extra $250 million in property taxes for pensions. Shouldn't teachers kick in, too?” He could also ask, “Why should teachers making an average of $75,000 a year for a 10-month job get a free pension. Do you?”

I think we know how most taxpayers would answer.

Under the contract proposal that Lewis agreed to submit earlier this year to her Big Bargaining Team, which then summarily rejected it, teachers over four years would have come out ahead. The deal would have given them 8.75 percent raises over four years in exchange for teachers beginning to pay 7 percent of salary for pensions. And in three of those four years, most teachers would have received lucrative “step and lane” pay hikes above the across-the-board raises.

That doesn't mean a little extra cash can't be found somewhere. The city's tax-increment financing pot has been refilled after a really good tax year, though only a little.

You've got to know when to fight and when to throw in the towel. Here's hoping both the CTU and the mayor have learned that lesson.