RALEIGH — Walt Disney was no stranger to adversity. He grew up in a large, itinerant family of modest means. His first film studio went bankrupt. But Disney never gave up. And he never stopped learning from his mistakes.

“All the adversity I’ve had in my life, all my troubles and obstacles, have strengthened me,” Disney once said. “You may not realize it when it happens, but a kick in the teeth may be the best thing in the world for you.”

Celebrating the virtue of perseverance may sound old-fashioned. In reality, however, it is a sound application of modern social science. In education, for example, there is a growing empirical case for the proposition that if we ask more of our children instead of trying to protect their supposedly fragile egos, they are more likely to enjoy success in school and beyond.

A new study of grading practices right here in North Carolina has gained significant national attention. Seth Gershenson, an associate professor at American University’s School of Public Affairs, looked at the records of some 350,000 North Carolina eighth- and ninth-graders who were enrolled in the state’s Algebra 1 course from 2006 to 2016. Gershenson chose these students because they had the same teacher for the whole year and were required to take an end-of-course test to assess their mastery of the subject.

For all 8,000 public-school teachers covered in the study parameters, Gershenson averaged the grades they gave their students and used a variety of statistical controls to adjust for student background and prior performance, teacher background and credentials, and other variables that might influence the grade averages. He then compared those average grades to the performance of the same students on the end-of-course test for Algebra 1.

The idea, in other words, was to see if the students of tougher-grading teachers were more or less likely to succeed than were students of easier-grading teachers — all other things being held equal.

Gershenson’s results suggest that tougher grading practices are an example of “tough love.” By expecting more at the front end as a student takes Algebra 1, the teacher makes it more likely that student will eventually achieve mastery in the subject. On average, students assigned to the toughest-grading quartile of North Carolina teachers scored 17% of a standard deviation higher on the exam than if those same students had been assigned to the easiest-grading quartile of teachers.

That’s not a small effect. “To put this difference in perspective,” Gershenson wrote, “consider that it amounts to a little more than six months of learning. It is also larger than the impact of a dozen student absences or replacing an average teacher with a teacher whose students consistently outperform expectations.”

Even moving from the easiest-grading 25% of teachers to one of the middle quartiles still boosted student learning by a significant amount. Gershenson also found that having a tough-grading teacher for Algebra 1 made it more likely a student would do well in subsequent math courses such as Algebra 2 and Geometry. And the benefits of higher academic expectations extended across all racial and family backgrounds.

That last point is particularly important in light of another of Gershenson’s findings: tougher grading standards are not equally distributed across public schools. Suburban schools and those with relatively low shares of poor students tend to have teachers who give lower grades. Rural and high-poverty schools tend to have teachers who give higher grades.

It is at least conceivable that teachers and principals in the latter groups of schools worry that rigorous grading might discourage students who are already facing significant challenges to their academic success. Their concern may be well-motivated but this study shows that acting on that concern is not well-advised.

As North Carolina students leave high school for college or the workplace, what matters most is how well they retain and apply what they’ve learned, not how students feel about themselves. Easy grades early in life can set them up for a hard landing.

John Hood is chairman of the John Locke Foundation.