Here’s a bit of advice to America’s teachers: If you want the nation’s opinion leaders and CEOs to like you, don’t congregate in groups. Everyone, it seems, loves teachers individually. But when they get together, they become a menace to civilization.

That’s one of the clearest take-aways from the just-concluded teachers strike in Chicago. Editorial boards from the right-wing Wall Street Journal to the liberal New York Times were nearly unanimous in condemning the seven-day strike. The Chicago Teachers Union was depriving the city’s children of their right to an education not just during the strike, editorialists argued, but also every day — by refusing to bow down to standardized tests. In the eyes of our elites, such tests have emerged as the linchpin of pedagogy and the best way to measure teacher, not just student, performance.

The unrelenting attack on teachers unions has some measurable consequences, too. This is evident from the fact that more than 90 percent of Chicago teachers voted to authorize the strike and that the union’s governing body so mistrusted the administration of Chicago Mayor Rahm Emanuel that it took two additional days to go over the proposed contract’s fine print.

The presumably numbers-driven educational reformers are highly selective when it comes to which numbers they take seriously. For years, many have touted charter schools (which usually are not unionized) as the preferred alternative to (unionized) public schools. But the most extensive survey of student performance at charter schools, from Stanford University’s Center for Research on Education Outcomes, found that, of the 2,403 charter schools tracked from 2006 to 2008, only 17 percent had better math test results than the public schools in their area, while 37 percent had results that were “significantly below” those of the public schools and 46 percent had results that were “statistically indistinguishable” from their public-school counterparts.

There’s also a good amount of data — including a study of high-performing public schools from the National Center for Educational Achievement — showing that ongoing teacher collaboration and mentoring and using tests for diagnostic, rather than evaluative, purposes produce better outcomes than the reformers’ brand of measuring teacher and student performance. The Cincinnati school district, which measures teacher performance chiefly through repeated peer evaluation, has the best student performance of any big Ohio city.

The Century Foundation’s Greg Anrig has argued in Pacific Standard magazine that reducing teacher evaluations to standardized tests amounts to subjecting education to Taylorism — the time-and-motion studies that so entranced corporate managers (and even Lenin) in the early 20th century and that boiled down worker performance to basic, repetitive tasks. A more successful management ethos, Anrig says, has been propounded by W. Edwards Deming, who argued that competitive performance evaluations eroded the social capital and trust successful institutions require. Deming’s more collaborative methods were taken to heart in postwar Japan and inform management practices at a range of successful companies, including Ford and Kaiser Permanente. As the example of Cincinnati suggests, they also work pretty well in schools.

There are other data that “educational reformers” would do well to study. Last week, the Illinois political newsletter Capitol Fax commissioned a poll of Chicago voters that showed that fully 66 percent of parents with children in the city’s public schools supported the strike, as did 56 percent of voters citywide. The only groups that disapproved of the strike (narrowly) were parents of children in private schools and whites. (Blacks and Latinos supported it.)

Given what we know about the cost of private schools and the demographics of Chicago’s public schools (87 percent of students come from households below the poverty threshold), it’s safe to say that the school reform movement hasn’t converted many outside the upper middle class. I suspect that a number of parents with kids in the city schools may have a more direct understanding of the challenges, both in school and out, that their children confront, as well as a clearer perception of the lack of resources that bedevil the schools.

Teaching, at least in major cities, is also a profession in which minorities are heavily represented; when reformers argue that we need to take down teachers unions to give more opportunity to minority youth, the argument veers perilously close to “We need to destroy the black middle class in order to save it.”

As both policy and politics, the demonization of teachers unions is a dead end for improving American education. Working with, not against, teachers is the more sensible way to better our schools.

Harold Meyerson is editor-at-large of The American Prospect.