Chicago school kids may be returning to classes this week after the first teachers strike in 25 years. As often happens, national attention was focused here for several reasons, among them the visibility and prominence of Mayor Rahm Emanuel, who probably suffered his greatest loss as a result of the strike.

Furthermore, one big contentious element—teacher evaluation methodology—is at the heart of the nationwide struggle over public education.

Emanuel, who likes to think of himself as a pragmatic, progressive Democrat, stuck his thumb in the eye of the Chicago Teachers Union from the moment he took office a year ago—winning in a landslide without the help of public unions.

He rescinded a promised 4 percent pay raise for teachers, ginned up promotion of charter schools, extended the school day by two hours with neither compensatory pay nor explanation of educational content and went to the legislature with his wealthy anti-union friends to require what was thought to be impossible, a 75 percent vote by union membership before a strike could be authorized.

When the strike vote came, more than 90 percent of the teachers said “yes,” recognizing that Emanuel was trying to position himself as sort of a Democratic rendition of Wisconsin Gov. Scott Walker. He talked tough with CTU President Karen Lewis—reportedly dropping one of his famous F-bombs on her—but found an adversary equal in smarts, toughness and commitment, which probably drove him nuts.

Now he is suing to end the strike.

Teacher strikes are rarely popular with parents, but here a majority favored the teachers while only 19 percent approved his handling of it, with much of his support coming from Republicans like Romney and Ryan.

He had to yield on some big issues.

The bottom line, however, is that Emanuel is out of the running as a presidential or vice-presidential candidate in 2016—a goal many believe he sought. While he might get re-elected mayor without labor support, it’s virtually impossible for a Democrat seeking national office and labor detests him.

Top among the big issues is teacher evaluation, which Emanuel and education technocrats (known as “reformers”) want based on student performance on high-stakes reading and math tests. At best these tests fail to reflect any true measurement of a rounded education; at worst they lead to teaching to the test and widespread cheating as we have seen around the country.

The teacher is only a tiny part of many factors ranging from home life, poverty, hunger and violence that affect a kid’s scores. To base teachers’ performance on such imperfect devices compounds the error.

Teacher evaluation is vital but complex. I refer you to a major Economic Policy Institute study on the topic, which includes serious recommendations from leading figures in progressive education that I do not have the space to summarize.

The strike and small concessions won on teacher evaluation may be the thrust needed for a national revaluation. That’s only fitting to come from the town where teacher unionism was born.

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Don Rose is a regular columnist for the Chicago Daily Observer