Whether it’s taking up a pencil and paper, or firing up a PC or an iPad, one of the fundamentals of taking a test is that everybody in a class takes the test. That is why a nascent movement to “opt out” of the new state accountability tests is a disaster for schools, taxpayers and students.

From the beginning, a worry about introducing high-stakes tests into Louisiana schools was the possibility of cheating. By and large, those worries haven’t translated into major problems. There has been no major cheating scandal such as that engulfing Atlanta schools a few years ago.

And the accountability system was set up from the beginning so that all students would take the high-stakes LEAP tests. Obviously, a school might want to manipulate the scores by encouraging a poor student not to take a test. That is avoided by giving a zero to students not taking the tests.

That’s the same principle for the new tests that this week replaced the old LEAP tests. But at least some parents, and a few school systems, have urged the state to allow “opt outs” for the new tests.

We believe the state Board of Elementary and Secondary Education is quite right not to give protesting parents a pass on testing. If the test results are to be valid, all the students have to take a test. For the taxpayer who has no children in public schools, the school performance score is the only way to get a statistical reading of whether taxes are being effectively spent.

What’s the argument this year? The new tests, PARCC for a short form of a long name, are aligned with new and higher academic standards, called the Common Core.

Amid much hullabaloo, Common Core has become a cause to some parents, who have forbidden their children from taking the new tests.

That this is bad for a student and a school is pretty obvious, as both get a goose-egg on their report cards. But it’s also bad for taxpayers, because the data to hold schools accountable is corrupted.

Back when Gov. Bobby Jindal was an enthusiastic advocate for Common Core — before he found out there are some right-wing constituents opposed to it — there was long-standing opposition to high-stakes testing. The new agitation is thus a combination of left and right, including those who believe students are overtested already. Nevermind that PARCC tests replace LEAP tests. It does not add a layer of tests.

Unfortunately, there are also some who believe fantastic theories that Common Core is some plot by the U.S. government, or Communists, or both, to take over control of local schools. That is why in some conservative circles there is an agitation against Common Core.

This is not about parental responsibility, but about political irresponsibility.

Opt-outs have been few despite the agitation on Common Core by Jindal and other political figures. We’ll know more once the testing period concludes. But the credibility of school accountability depends on students taking the tests.

That must be the fundamental policy of the state, and of teachers in every classroom, because the consequence is scuttling back to decades of social promotion: A student aged out of a grade is no smarter than when he started it.