Continued from page 1

Union leaders point out that other factors beyond evaluations are also at play. Chicago teachers are seeking a 30 percent pay raise over the next several years, and have also demanded better facilities; specifically, air conditioning in every classroom.

“Collective action was the only way improve their schools, their communities and their students’ education,” Randi Weingarten, president of the American Federation of Teachers, said earlier this week. The Chicago Teachers Union (CTU) is a subsidiary of the AFT.

“We know that the members of the CTU are prepared to stay on the picket lines,” she continued. “We also know they would rather be on the job, in the classroom educating their students. … The students, teachers and educational support staff — and the city of Chicago — deserve a school system that works for everyone. In the end, that is what this strike is all about.”

In years past, some analysts say, leaders such as Mr. Emanuel, Mr. Villaraigosa and Mr. Bloomberg could simply settle their differences with the union by doling out cash. If, for example, mayors or school administrators wanted to implement a controversial teacher-evaluation system, they could persuade the union to agree to it by raising salaries, said Mr. Petrilli, the Fordham Institute analyst.

“The way you got unions to sign off on the reforms you want without going to the point of a strike is to buy them off,” he said. “But districts are broke. They no longer have the money to buy off unions.”

The dire financial situation of local and state governments has led to bold attempts to forever change the balance of power in public schools. Wisconsin Gov. Scott Walker, a Republican, mounted the first challenge to the collective-bargaining power of teachers, a success that drew the ire of labor across the nation.

Ohio Gov. John Kasich, also a Republican, followed suit, though voters later rejected his proposals through referendum.

Going forward, Mr. Petrilli said, more leaders — whether they be Republicans or Democrats — may realize there is another option beyond giving union teachers more money or risking a strike.

“In many cases, there’s more running room than they think they have,” he said. “But it takes some political calculation. You have to put yourself out there and become vulnerable.”