Poudre High School senior Emily Tashea joins a protest against the current standardized testing in Denver, CO March 7, 2015. Photo: Craig F. Walker / The Denver Post

In 2010, Diane Ravitch, an activist for the most militantly anti-reform wing of the teachers-union movement, wrote a Wall Street Journal op-ed proposing that Republicans use their newfound control of the House of Representatives to roll back the Obama administration’s education reforms. Since then, the union backlash against the Obama administration’s agenda has gained force. Yesterday, it manifested itself in a Senate vote in which Republicans and the unions worked in more open cooperation – against the Obama administration and civil-rights groups allied with it – than at any time in the past.

You should read Libby Nelson’s terrific explanation of the dynamics behind the vote. The gist of the alliance is that both the Republicans and the unions want to reduce the federal government’s ability to direct the course of education policy. Nelson detected an interesting rhetorical confluence:

Sen. Lamar Alexander, the Tennessee Republican who now leads the Senate education committee, has a favorite epithet for how Duncan has used his power. Alexander is fond of saying that Duncan created a “national school board.” Eskelen García echoed Alexander, hardly an ideological ally, in a Thursday interview. “Nobody elected the education secretary to be the national superintendent of schools or the national school board,” she said.

What makes this alliance significant is that Republicans and the unions have joined not only to defeat a common enemy but in support of a common principle: local control. In this case, local control means that schools should be free of accountability requirements from Washington that force them to measure student and teacher achievement. Those accountability measures, which the Obama administration has spread through its Race to the Top grants and use of waivers from No Child Left Behind to encourage states to reform their education policies have unsettled traditional union contracts. The Obama administration’s reforms have forced schools to differentiate between effective and ineffective schools and effective and ineffective teachers. Unions prefer traditional contracts that pay teachers on the basis of seniority rather than effectiveness, and make it difficult or sometimes functionally impossible to fire ineffective teachers.

Ravitch’s Journal op-ed uses the word “local” seven times, and argues that many in Congress “understand that their public schools are the heart of their community and that local problems are best addressed by local solutions.” She shrewdly recognizes the instinctive Republican affinity for this principle. Liberals, of course, tend to oppose local control, because it often leaves policy in the hands not of the people, in some Norman Rockwell–esque way, but local powers. And in the case of education policy, teachers unions generally wield far more power than a local school district can match. Only interference from a more powerful outside force — like state government, or the federal government — can counterbalance that influence. The unions and the Republicans have spent so many years thinking of each other as enemies that they have been slow to recognize their alliance, and some of them have flinched uncomfortably from it. But the logic of the alliance has made itself increasingly evident.