Eleven New York City education reporters were huddling on e-mail last October 20, musing over ways to collectively pry a schedule of school closings out of a stubborn press office, when the chatter stopped cold. Word had filtered into their message bins that the city was about to release a set of spreadsheets showing performance scores for 12,000 of the city’s 80,000 teachers—names included. Few understood better than the beat reporters that this wonky-sounding database was a game changer.

The Los Angeles Times already had jolted newsrooms across the country back in August, when it published 6,000 public school teachers’ names next to its own performance calculations. New York education reporters, though, were considerably more reluctant to leap on this bandwagon. They found themselves with twenty-four hours to explain a complex and controversial statistical analysis, first to their editors and then to the public, while attempting to fend off the inevitable political and competitive pressure to print the names next to the numbers, something nearly every one of them opposed. “I stayed up all night kind of panicked,” said Lindsey Christ, the education reporter for the local NY1 television station, “writing a memo to everyone in the newsroom explaining what was coming and what was at stake.”

It may seem odd that a geeky algorithm has become such a hot topic in education, but it is another indication of how a group of well-connected newcomers to the contentious world of education policy has influenced the national conversation on the subject. As a group—mostly Wall Street financiers, political lobbyists, and venture philanthropists—they are drawn to the tools and terms of business economics. In this case, that means something called “value-added metrics,” which estimate the worth of a teacher by analyzing her students’ test scores over time.

Supporters of this technique argue that teacher evaluations require objective rigor, calculated with statistics. Weak teachers, they argue, should not hide behind a subjective, protective system that undermines children’s futures. Critics counter that the calculations are incomplete, misleading, and often wrong. Teachers wonder how a number built on test questions can capture what it takes to help a student wrestle with ideas, say, or learn to write with voice. Wouldn’t it make more sense, they ask, to use student work, peer mentoring, and rigorous classroom observations for a more meaningful evaluation? Economists on all sides of the debate agree that these stats cannot paint a whole picture of effective teaching. So, the critics say, why print them indelibly next to teachers’ names?

But numbers have an allure. Governors and mayors facing huge budget cuts are demanding easier ways (read: rankings) to fire the worst teachers and reward the best. Washington likes numbers too. In the past year, eleven states including New York, Florida, and North Carolina have agreed to use student scores to evaluate teachers in exchange for federal Race to the Top grants.

So perhaps it was inevitable that elements of the free-market reform movement would land in the laptops of New York’s education reporters, with enough force to diminish the quality of the conversation about the city’s public schools.

The battle over the numbers is in part a battle over control. For decades, neither of the two national teacher unions has done enough to shed their more arcane rules, which has made innovation difficult. Still, the assault surprised the unions at first, mostly because it came from unexpected places, including the press. Steven Brill’s lopsided 2009 piece, “The Rubber Room,” in The New Yorker, was among the first to frame the current reform climate. He portrayed a war between good-guy marketplace reformers and villainous unions, blistering the UFT, the United Federation of Teachers, for its part in negotiating rules that led to the city’s practice of warehousing tenured teachers faced with discipline cases into “rubber rooms,” with little to do but punch the clock. The powerful union deserved the ridicule. Still, Brill allowed Schools Chancellor Joel Klein, the story’s white-hat protagonist, to dance around the irony that he had been in charge of the system, and thus the so-called “rubber rooms,” for seven years.

When eliminating teacher tenure became the movement’s silver bullet, a March 2010 Newsweek cover story jumped on the cause: “The Key to Saving American Education: We must fire bad teachers.” That followed an iconic 2008 Time cover that established then-DC school chancellor Michelle Rhee as the movement’s celebrity executive. Rhee was pictured broom in hand, poised to sweep bad teachers away.

LynNell Hancock is the H. Gordon Garbedian Professor of Journalism at Columbia, and director of the school's Spencer Fellowship in Education Journalism.