This country and state used to argue about whether kids were getting too many standardized tests and whether those tests were well-designed. That was a useful argument.

But in recent years, it has taken a bizarre twist: Small-government conservatives and some teachers unions have joined forces in attacking, not the frequency or quality of state tests, but the very requirement that kids take them. Some like-minded parents have signed on to a union-championed “opt-out” movement aimed at ginning up a broad boycott of assessment exams.

The notion that standardized tests are harmful is an uncommonly dangerous idea.

The real world demands standardized tests. People must pass state-mandated tests to become electricians, doctors, truck drivers, real estate agents, cosmetologists, massage therapists, etc. etc. Yet anti-test extremists expect the public to believe that statewide assessments don’t belong in schools – of all places.

Attacks on testing usually begin by invoking the flaws of No Child Left Behind law, the 2002 education law that set ridiculously unrealistic test-based goals for schools and threatened penalties if they failed to meet them. Because they were tied to the impossible mandates, the tests themselves suffered guilt by association.

Congress is now gearing up to overhaul or revise NCLB. It should dump the unworkable parts of the law. It should not dump the federal requirement that states administer standardized tests from the third through the eighth grades and once in high school.

Many of the nation’s leading civil rights organizations, including NAACP, the National Urban League and National Council of La Raza, recently issued a joint statement opposing repeal of the federal test mandate.

They know what’s really at stake here. Until No Child Left Behind and its maligned tests came along, it was all too easy for some school districts to disguise the poor performance of minority students. The law exposed achievement gaps across the country by requiring districts to give the tests and publish the scores – broken down by ethnicity and poverty.

The effect was galvanizing. Communities and states suddenly discovered disparities that had been hidden behind statistical averages. Many of them took action – and the performance of poor and minority kids has subsequently improved.

Take away the tests, or water them down enough, and we’re back to the days of guessing and hoping.

In Congress, the opposition to the testing mandate is likely to be driven less by unions and more by conservative ideology. Some Republicans don’t like the idea of the federal government having any role in public schools, period. They, too, want the test requirement gone.

This should not become a partisan issue. As George W. Bush and Sen. Ted Kennedy recognized when they negotiated the original law, there’s no red-blue divide over whether children should get the best possible education.

Sen. Patty Murray of Washington will be a leader in the overhaul of NCLB. She struck exactly the right tone in a floor speech two weeks ago:

“We know that if we don’t have ways to measure students’ progress, and if we don’t hold states accountable, the victims will invariably be the kids from poor neighborhoods, children of color and students with disabilities …”

“And if a school is consistently failing to provide a quality education years after year, parents deserve to know.”

Misguided as they are, opponents of standardized tests are passionate. People who want accountable schools must stand up for testing with the same fervor.