Each year, the Chicago Public Schools system (CPS) spends over $13,000 per student in order to graduate 60 percent of its 400,000 students. In an attempt at reform, Mayor Rahm Emanuel has pushed to increase teacher accountability and extend the system’s school day, which at 5 hours and 45 minutes is currently the shortest of any city in the country. The Chicago Teachers Union (CTU) has responded with a tantrum and on Monday launched a strike that’s capturing election-season headlines.

The dispute has national import because its outcome will have national implications. The mayor, President Obama’s salty-tongued former chief of staff, is challenging the CTU to accept the same kinds of reforms that the president has championed, and the contretemps has highlighted the tension between teachers’ unions and Democratic reformers.

Unlike the many mayors, school boards, and superintendents who have folded at the first sign of union displeasure, Emanuel has stood tall. Even though this has meant possibly dragging the president into a nasty intraparty battle, Emanuel has sought to do right by Chicago’s students and taxpayers. Good for him.

The district and the union are stuck on four main issues: salary, class size, the length of the school day, and teacher evaluation. In the midst of a municipal fiscal crunch, the CTU initially demanded a 30 percent raise over the next two years. The district countered with a proposal of 16 percent over four years, plus paid maternity leave, if teachers agreed to a more expansive accountability system. (And this is all in addition to the seniority-based raises in the city’s “step and lane” pay system, which already guarantees teachers steady annual increases based on experience.)

The CTU wants the district to hire more teachers and reduce class sizes, even though CPS already employs one teacher for every 16 students. The CTU also wants priority hiring for recently laid-off teachers, regardless of their classroom performance. Meanwhile, Emanuel has called for giving school administrators more discretion when it comes to selecting their own staff, and an accountability system in which student test scores account for 25 percent of teachers’ evaluations. The union has stood steadfastly against the accountability provision.

Emanuel is right to push back against demands for more staff and higher salaries when the city is projected to have a budget deficit approaching $1 billion. But even if Chicago had the money to hire more teachers, smaller class sizes aren’t even the best way to spend it on schools. A RAND Corporation study of the class-size-reduction plan in California in the late 1990s found that any gains made in classrooms by good teachers’ teaching fewer students were offset by losses for students moved into classrooms where lower-quality teachers were hired to meet the required ratios.

While the mayor deserves some praise, his push for teacher-evaluation reforms illustrates the risks posed by the one-size-fits-all thinking of too many progressive reformers, Emanuel and Obama included. The unions are right to be concerned that teacher evaluations that rely too much on math and reading scores and tens of thousands of cookie-cutter, bureaucratic observations may be unreliable or inaccurate, distract from teachers’ other responsibilities, and press teachers to narrow instruction to reading and math. Today’s one-size-fits-all teacher-evaluation systems that the president supports are not well suited to online learning, new school models, or allowing for entrepreneurial approaches to using teachers and technology.

But Emanuel and Obama’s original instincts here are still good. They’re right to push for reforming the existing and anachronistic accountability systems that rated 99 percent of teachers “effective,” but they stumble when they succumb to the progressive temptation to solve every problem through a new bureaucratic diktat. A longer school day and a better evaluation system are worth fighting for, but they should not be arbitrary sweeping reforms implemented wholesale on a sprawling municipal bureaucracy.

This fight also puts President Obama in something of a pickle. He can’t walk away from his union base, but he can’t look like he’s giving up on the kinds of reforms he has championed, especially when his former chief of staff is pushing them. If the unions cave, this story, combined with the failure to recall Scott Walker, would make 2012 one of labor’s bleakest years in memory. But if Emanuel appears to give in, even tough-talking Democrats might begin to have doubts about the consequences of education reform, dealing a blow to the president’s policy agenda. As for Obama, his best result would be a quick and quiet resolution to this whole mess, so that everyone can get back to talking about Mitt Romney’s taxes.

Frederick M. Hess is director of educational-policy studies at the American Enterprise Institute. Michael Q. McShane is a research fellow in education policy at AEI and author of the just-published book President Obama and Education Reform: The Personal and the Political.