In 1993, when Travis Hofmann was a freshman of 15, he had traveled little beyond the sand hills that surrounded his hometown, Alliance, Neb. He was the son of a railroad engineer, a trumpeter in the high school band, with a part-time job changing the marquee and running the projector at the local movie theater.

In Travis’s class in global geography at Alliance High School, however, the teacher introduced the outside world with the word and concept of genocide. The teacher, Tim Walz, was determined that even in this isolated place, perhaps especially in this isolated place, this county seat of 9,000 that was hours away from any city in any direction, the students should learn how and why a society can descend into mass murder.

Mr. Walz had already taught for a year in China, and he brought the world into his classroom in the form of African thumb pianos and Tibetan singing bowls. For the global geography class, he devised something far more ambitious than what the curriculum easily could have been  the identification and memorization of capitals, mountain ranges and major rivers. It was more ambitious, too, than a unit solely on the Holocaust of the sort many states have required.

“The Holocaust is taught too often purely as a historical event, an anomaly, a moment in time,” Mr. Walz said in a recent interview, recalling his approach. “Students understood what had happened and that it was terrible and that the people who did this were monsters.