Without a consistent way to measure student performance in Massachusetts, it’s easy to predict what would occur. Thriving suburban districts would keep thriving. But with no uniform standard for identifying student weaknesses, some kids in underperforming schools would be left without the knowledge and skills they need to succeed at work or college.

Yet, watching the maneuvers of the Massachusetts Teachers Association during the COVID-19 pandemic, one could easily come to the conclusion that the state’s largest union is more concerned with getting the MCAS graduation exam — the state’s main tool for assessing schools’ performance — out of their classrooms than students back in them.

A recent missive from MTA president Merrie Najimy urges MTA members to “inform parents and guardians of their right to opt their children out of testing’’ and to rally round a bill “that would end the MCAS-based graduation requirement.’’

Because the test spotlights schools that need improvement, teachers unions (and some school districts) have never much liked it. But the MTA has now elevated its anti-MCAS campaign to new levels of irresponsibility. Democratic lawmakers should not be enabling or encouraging that effort.

On the former matter, the MTA is leading its members down the pedagogical primrose path regarding the Massachusetts Comprehensive Assessment System exams. In fact, there is no such right to opt out of the MCAS, says Colleen Quinn, spokeswoman for the Executive Office of Education. “Every student in grades 3-8 and 10th is required to take the test,’’ she said.

Filed by Senator Joanne Comerford, Democrat of Northampton (and a former campaign director at MoveOn) and Representative James Hawkins, Democrat of Attleboro (and a former Senate district coordinator for the MTA), the MTA’s favored legislation would do away with the test as a graduation requirement and establish a procedure to develop alternative methods of determining student competency. The process alone would make Rube Goldberg green with envy. The bill calls for 25 school district task forces, co-chaired by the local school board chairman and the local teachers union president, which would develop recommendations for consideration by the Massachusetts Consortium for Innovative Education Assessment, a union-and-district partnership that opposes the MCAS. The consortium (with the help of an advisory council that would include eight members of the district task forces, with the stipulation that two of those members be appointed by the teachers union) would have two years to issue a report to the Department of Elementary and Secondary Education for new competency-determination methods. The predictable result would be to jettison the MCAS in favor of assessment methods that wouldn’t allow meaningful cross-district comparison. At least 32 Democratic legislators have signed aboard as co-sponsors.

That comes on top of MTA efforts to insert a 2021-MCAS-suspending rider into the state budget. Last year, just a few months into the pandemic, the union tried to make eliminating the MCAS graduation requirement a condition of teachers returning to school.

In a statement to the Globe about its anti-MCAS initiatives, Najimy noted that though the union’s anti-MCAS efforts had preceded the pandemic, “the pandemic has laid bare the structural racism at the root of inequities in opportunities and resources in our communities of color.’’

A more apt summation would be that the union is using the pandemic to outfit its long-time anti-MCAS quest in the garb of racial justice. Contending that the MCAS exams have “implicit biases,’’ Najimy continued: “It is long past the time when we should have stopped using them [the exams] to label children of color with racist and dehumanizing terms such as ‘underperforming’ or to focus on manufactured ‘achievement gaps’ and ‘colossal learning loss.’ These labels and terms hearken back to the false eugenics narrative that people of color are intellectually inferior.’’

That is both misleading and denigrative. The underperforming label, of course, is applied to schools, not students. It is certainly true that the MCAS has revealed achievement gaps between different racial groups. (That hard-to-close gap is something Comerford seems sincerely concerned about.) But the MCAS did not, to use Najimy’s term, manufacture the achievement gap; the multi-subject exams merely revealed it for all to see. Nor will nixing the MCAS as a graduation exam close the gap; that action would simply reduce the attention paid to differential rates of achievement.

Further, Najimy’s attempt to reframe the union’s anti-MCAS stance as a matter of racial justice ignores a signal fact: The education reform effort in this state was a bipartisan quest by people of good will and good intentions — prominent among them several progressive Democrats — to improve educational quality for all students.

“It’s both preposterous and despicable that MTA would seek to wrap its anti-accountability campaign in the mantle of racial justice,’’ said Paul Reville, a professor at Harvard’s Graduate School of Education who served as secretary of education under Governor Deval Patrick and has been an instrumental figure in the state’s quarter-century education-improvement effort. “The primary purpose of education reform in Massachusetts was and is equity. MCAS shines a light on how much students are learning. It highlights those Black, brown, and other students who are being failed by our education system. It calls attention to their challenges and provides a rationale for giving teachers support they deserve to help their students meet high standards.’’

Now, the MCAS is hardly perfect or foolproof.

But any legislator committed or paying lip service to the MTA’s effort to end the exam as a graduation requirement should educate themselves about this state’s long and largely successful effort to improve educational quality. Prior to the state’s landmark 1993 education-reform law, there were no statewide curriculum standards for public school students. Nor was there a way to tell, beyond the somewhat subjective and self-interested assessment of teachers, whether students were mastering necessary subjects.

The result was that many students graduated from high school without the skills needed for success at work or college. The state’s education-improvement effort created a broad consensus for pairing higher spending with higher standards. As the accountability part of that bargain, the MCAS exams provide a measurement of student achievement that allows comparisons between schools, districts, and demographic cohorts. That approach has paid off, boosting Massachusetts to a nationally recognized (and nationally envied) position of leadership on public education.

The MCAS has, however, created a (locally) unwelcome focus on underperforming schools. It has also aroused the ire of teachers unions by allowing a data-based way to identify poor schools. In subsequent education legislation, the Legislature gave the state commissioner of education enhanced authority to force changes in those schools, sometimes by pushing to alter aspects of the local union contracts. Because those efforts are based on a school’s MCAS scores, state interventions have also heightened union opposition to the MCAS.

Now, it’s a natural tendency of unions to want to shield their members from change, accountability, and competition. That, however, is where legislators should be expected to display some backbone. Moving to the sort of system the MTA advocates, where there is no uniform standard to judge whether students have mastered their coursework, runs the very real risk of letting nation-leading Massachusetts lapse back to its pre-education-reform days.

That’s not to say the MCAS shouldn’t be periodically re-examined. Occasionally a question turns up that is racially or culturally objectionable or oblivious; those questions, obviously, should be expunged. It’s also worth considering complementary measures of student performance. But Paul Toner, president of the MTA from 2010 to 2014 (and the union vice-president before that), makes two important points about such an effort.

First, eliminating any uniform standard by which students can be assessed risks undermining the broad statewide consensus that supports the large budgetary investment Massachusetts has made in its schools. Second, any alternative competency-determination standard should be developed and evaluated before, not after, eliminating the MCAS as a graduation requirement.

“You need to have the alternative first,’’ said Toner, now senior director for national policy and partnerships at Teach Plus. “You don’t stop the train while you figure it out.’’

That message, from a well-regarded former MTA president who hails from an era when the MTA was considered a collaborative and serious-minded partner in education-improvement efforts, is one MTA members need to hear today. Democratic legislators, meanwhile, need to send a clear message of their own. Yes, the MTA may be a valued member of the party’s electoral coalition, but when it comes to education policy, lawmakers have to put the considered best interests of the state’s schoolchildren above union concerns.

Editorials represent the views of the Boston Globe Editorial Board. Follow us on Twitter at @GlobeOpinion.