More than any test in my first 13 years of school, I will forever remember the one in May 1970 that Mr. Mullins canceled. We had spent the preceding weeks diagramming sentences. I was poised for any tangle of an attributive adjective or predicate nominative he could throw at me. But what Mr. Mullins decided to diagram instead that spring day was the history of a war.  

With the frenetic care of a physicist laying out an equation, he began at the far end of a chalkboard with the rise of Ho Chi Minh as revolutionary leader of the Viet Cong and their routing of French colonialist forces at Dien Bien Phu in 1954. Noting the country’s strategically important trove of rubber for a rising China, he marked the first dispatch of US military advisers by President John F. Kennedy in 1961. Then, scratching pivotal battle after pivotal battle onto the slate, Mr. Mullins tracked the Viet Cong’s endurance against Agent Orange, napalm, and the steady escalation of carpet bombing and troop levels (385,000 at their highest) by three presidents. 

With a trail of shattered chalk at his feet, Mr. Mullins concluded his history, two room-long blackboards later, with the four Kent State University students who were gunned down by the US National Guard earlier that week while protesting the war.

For our yearly guide to the region’s schools, we invited students and teachers to reflect on what they are learning, both academically and not (“What I Learned”). For me, even decades later, Mr. Mullins’s momentary switch from English to History remains the lesson that most changed my life. 

For years, I had watched the war unfold on the nightly news, the growing count of American casualties displayed like a basketball score next to ABC anchor Howard K. Smith’s solemnly talking head. My mom, a Goldwater Republican, would tsk-tsk and offer, “I don’t know why we don’t bomb that country off the map.” My dad, a former World War II B-17 ball-turret gunner (who, by any statistical measure of those who had done his job, should not have survived), sat rigid and silent. A year before, after becoming my sixth-grade class’s debate champion, I had taken on our teacher. The subject: the My Lai Massacre. I picked my side: a defense of Lt. William Calley, the man who led a “search and destroy” mission that left 300 women and children dead. My argument: he was following orders. 

That spring day was not the first time Mr. Mullins had canceled a test. The urge to forgo measuring our learning in order to inspire it overcame him many times, whether through an impromptu pageant of a Shakespeare play or his own mellifluous reading of Faulkner’s “The Bear.” In short, Mr. Mullins was cool. But the day he mapped the Vietnam War, he was angry and hurt. And watching his disappointment in his country unfold across the blackboard shook me into the sharpest early rediagramming of my own life: the moment I realized my parents and my country weren’t always right, and that, as one teacher in our survey so enduringly put it, “The teachable moment is often unplanned.”