The year 2020 will be remembered for many awful changes. But young people who don’t like school may recall it fondly as the Year of the Easy B.

Superintendents and principals have told teachers to be kind when filling out final report cards. The widespread feeling is that because the pandemic made a mess of learning this spring, honest grading should wait for better times.

So what are we to make of a remarkable study that came out in February, a month before the novel coronavirus turned assessment of students to mush? American University economist Seth Gershenson’s report “Great Expectations: The Impact of Rigorous Grading Practices on Student Achievement” is the most damning indictment of grade inflation I have seen in 20 years.

Analyzing grades given to 350,000 students by 8,000 Algebra I teachers in North Carolina, Gershenson discovered this: Students learned more from teachers with higher grading standards, on average performing better even two years later. Tougher grades improved the learning outcomes of all major student ethnic groups: black, Hispanic and white. Positive effects from tough grading were found in both rich and poor schools.

Why has there been so little research on this? Why do school reformers so rarely mention the perils of easy grading? The answer is obvious. This is a problem most of us have chosen to ignore. It would be too hard on relationships between students, teachers, parents and principals to take grading seriously.

Few scholars see the harm as clearly as Gershenson does.

“Low grading standards pose a grave threat to the performance and evaluation of U.S. public schools that ultimately jeopardizes the competency of high school and college graduates who are entering the workforce,” he said. “Assigning good grades for mediocre work signals to students that excellent work is beyond their reach. . . . When students who have not mastered the material receive passing marks anyway, they can become complacent and fail to reach their full potential. Lax grading is a pernicious practice that provides students and parents with a false sense of security and accomplishment.”

If you’re a parent and want to shrug this off as the teacher’s fault, take a look at the last major study of this problem, David N. Figlio and Maurice E. Lucas’s “Do High Grading Standards Affect Student Performance?” That 2000 report on elementary school report cards in Florida asked parents to grade their children’s teachers. Two-thirds gave the teachers A’s, but 50 percent were more likely to assign a grade of B or below to a tough grader than a relatively easy one.

Gershenson’s 48-page report, published by the Thomas B. Fordham Institute education reform think tank, compared eighth- and ninth-grade student Algebra I grades from 2006 to 2016 with their scores on North Carolina’s required Algebra I end-of-course exam. Teachers whose B students demonstrated greater mastery of algebra on the state tests were classified as having higher grading standards than teachers who assigned B’s to students who learned less.

In North Carolina during that period, more than one-third of B students failed to score proficient on the state algebra exam. The report includes excerpts from interviews by Fordham Institute staffers asking teachers throughout the country why grading standards are often so weak.

“This is awful to say,” one teacher said. “It’s easier to pass the kid than to actually really give valid feedback.” Another teacher quoted emails from parents saying: “I demand to know why my kid got a B. My kid has an A in all the other classes except yours.”

Michael Grill, a veteran social studies teacher at Wakefield High School in Arlington County, Va., told me “grading is a hot-button issue right now” because of his district’s guidance on grading during the school shutdown. Arlington, like many school systems, said teachers’ final course grades should reflect achievement before the schools closed, with maybe some sweetening. Arlington said teachers may boost a student by a full letter grade if the student submits “artifacts of their learning that would demonstrate proficiency with concepts that they were unable to demonstrate earlier in the school year.”

Not mentioned in that guidance is this much-ignored truth: Teachers are almost always free to inflate grades if they want. Principals rarely assess teachers on their grading standards. Parents and students rarely complain if grades are higher than expected. Grill said some teachers think the rules for this year provide “true remediation opportunities for students” while others think they are a way to avoid student and parent ire.

Gershenson noted this issue extends beyond middle and high school. Other studies, he said, find college students study as much as 50 percent less if they expect the average class grade to be an A — not so unusual in some cases — rather than a C.

His study of grading standards would have been impossible without having a standardized state exam with which to compare teacher grades. He warns that if such standardized tests are eliminated or not required for college admission, the pressure to inflate grades will only increase.

State tests (most of which won’t be given in 2020) as well as the SAT and the ACT are annoying, to be sure. But this year of easy grading is a good time to consider what American education is likely to become with even fewer standards.