In conferences, debates and panel discussions about schools, I await mention of the unmentionable issue: grading. It never comes.

We discuss tests, teacher assessments, Common Core standards and school ratings, but not student report cards, the greatest source of stress and miscommunication in our education system.

I opened Richard DuFour’s new book, “In Praise of American Educators: And How They Can Become Even Better,” expecting the same report card avoidance. DuFour is a celebrated consultant with long experience at an exceptional high school — Stevenson in Lincolnshire, Ill. — but he has to deal with the usual issues because that’s what he’s paid for.

But in the middle of the book, he surprised me. He launched a brilliant attack on the notion that tough grading will prepare students for the real world. So many of our educators, as well as the rest of us, think F’s build character and save struggling students from lives of sloth and poverty.

DuFour recommends that schools provide students who are not learning with extra time and support. This makes educators, particularly those in secondary schools, uncomfortable.

“One of their frequently expressed concerns is that giving some students additional chances to learn is ‘not fair’ to the students who passed the first time,” he says. “If the mission of the school is to identify students who learn fast and who learn the first time we teach it, this approach makes sense. But if the mission of the school is to ensure all students learn, it does not.”

Students “unable to demonstrate proficiency,” he says, should be “required to keep working and learning until they become proficient.”

School veterans often say to that: “Are you kidding?” DuFour says they tell him “providing students with these second chances won’t prepare them for the harsh realities of the ‘real world’ or the ‘sink or swim’ environment of higher education, where students are expected to take full responsibility for their learning; requiring students to get additional help until they become proficient simply ‘enables’ students to give less than their best effort.”

DuFour responds: How’s that working for you?

“How does the traditional practice of allowing an irresponsible student who would rather take a zero than do the work teach that student to act responsibly?” he asks. “How does allowing a student to opt out of a program to provide him or her with assistance teach responsibility? If a student is truly going to enter a sink-or-swim situation in higher education, the best preparation is to teach the student to swim — to provide the student with the knowledge, skills and habits essential to success in that situation — rather than allow the student to sink first in high school.”

Many of my fellow basic training draftees many years ago were not well motivated, but the Army — one of our nation’s most successful educational institutions — made clear we had no option other than to learn.

DuFour often hears, as I do, educators in schools with high failure rates say “the students won’t do the work.” Often they say without support at home there’s no hope. Instead, DuFour says, educators “must teach the skill by creating systems that place students in an environment during the school day where their work is monitored closely until it is completed and they can demonstrate proficiency.”

Sounds like good old Ft. Lewis, Wash., to me. But DuFour offers detailed descriptions of interventions that work without drill sergeants. And he makes the essential point: “There is virtually no research or evidence to suggest that higher incidents of failure in school produce higher levels of responsibility, greater academic achievement in college, or a higher likelihood of success in meeting the demands of adult life.”

Replacing F’s with passing grades for little work, one troubling explanation for our rising high school graduation rates, also is not good. In the new year, firm adherence to learning in our high schools would be a welcome change.