We are now in day 4 of the teacher strike in Chicago, which pits the Chicago Teachers Union against education reformers led by President Barack Obama’s former chief of staff, Chicago Mayor Rahm Emanuel.

It’s a decisive, complicated battle, made more complicated because Republican presidential candidate Mitt Romney says he’s opposed to the unions and their demands (or, rather, “ We stand with the children and we stand with the families and the parents of Chicago”). Emanuel’s former boss, president Obama, is keeping mostly quiet on this issue, because, of course, the teacher unions and their support is pretty essential for the Democratic Party.

Romney’s point seems valid, of course. Teachers’ strikes are bad for students. But the trouble is there’s not much evidence that the reforms Emanuel pushes are any good for students.

Recently Dylan Matthews of the Washington Post’s WonkBlog wrote about the evidence on strikes:

Two of the best recent studies on the effects of teacher work stoppages and strikes concern labor disputes in Ontario schools in the late ’90s and early 2000s. One, by the University of Toronto’s Michael Baker, compared how standardized test scores rose between grade 3 and grade 6 for students who lost instructional time because of the Ontario strikes, and for students who were unaffected.

And it’s not just Ontario. Michèle Belot and Dinand Webbink, now of the Universities of Edinburgh and Rotterdam, respectively, found that work stoppages hurt student achievement, increased the number of students repeating grades and reduced higher education attainment in Belgium. What’s more, studies dealing with teacher absences for reasons other than strikes bolster these findings.

This post became oddly controversial. Blogger Doug Henwood complained about some parts of the studies Matthews cited (particularly their failure to address the “larger context”) and wrote that:

The CTU’s strike, led by a vigorous reform leadership, is quite explicitly about lots more than the wages and working conditions of teachers. It’s about fighting the privatization and union-busting agenda of Chicago Mayor Rahm Emanuel—which he shares with other big-city mayors like Michael Bloomberg, as well as his comrade Barack Obama. By circulating bogus stories about the damage the union is doing to the children of Chicago, Matthews is offering cover to this odious agenda.

This is ridiculous. Obviously strikes hurt student learning. Factory strikes reduce the production of goods. Nursing strikes hurt health care. Sanitation workers’ strikes make the cities dirtier and more prone to disease. That’s sort of the point.

But as long as we’re on this whole “let’s cite some evidence” thing, it’s worth pointing out why the Chicago teachers are striking.

There’s some dispute about pay and health care benefits, but these issues are ultimately secondary to the major concern, which is that in March Chicago introduced a new evaluation system where 40 percent of teacher evaluations are based on standardized tests. The teachers union resists this, arguing that it’s too punitive and that standardized tests are designed to measure student progress, not teacher quality. Teachers also want to limit class size to 28 students.

This isn’t just about specific changes for Chicago school policy in 2012, however. The strike has a lot to do with the future of public education in the city. As Valerie Strauss pointed out over in another part of the Washington Post:

The reforms championed by Emanuel… include merit pay, an expansion of charter schools, teacher and principal assessment systems that are linked to student standardized test scores, a longer school day and job security for veteran teachers.

The problem, as Stauss explains, is that as far as Emanuel’s reforms go “there’s no real proof that they systemically work, and in some cases, there is strong evidence that they may be harmful.”

Those who oppose the teachers union do well to point out that their striking has been proven to hurt student learning. The teachers union, however, arguably has a much better point: we don’t know the things the city demands that we do will improve student learning either.

Daniel Luzer

Daniel Luzer is the news editor at Governing Magazine and former web editor of the Washington Monthly. Find him on Twitter: @Daniel_Luzer