It was 1979, and Nils Johnson-Shelton had a lot in common with a classmate named Etan Patz. Both were 6-year-old boys with bowl cuts, the sons of artists living in lofts in SoHo. They rode the same bus to the same elementary school, where they both attended first grade.

On the morning of May 25 that year, Etan went missing and was never found. His disappearance not only shocked New York City; it was later credited as the event that forever altered parenting, a word that had only recently entered the lexicon. From that terrible day, the notion that children in America should be left to their own devices — to run with their friends, climb trees, fall down, get up and keep running — changed. Parenting transformed, too, as mothers and fathers grew more intense, more fearful, more riddled with anxiety about threats, real and imagined, that children newly seemed to face.

“Etan’s case is foundational,” said John E. Bischoff III, a vice president at the National Center for Missing & Exploited Children. “It made parents more aware and concerned for their own children’s safety.”

The biggest change Mr. Johnson-Shelton recalls from his childhood was that he no longer rode the bus to school. Instead, he would clamber onto his father’s bike and the two of them would rattle across the cobblestone streets of TriBeCa.

“I was so young that I didn’t put the two together,” he said recently. It never occurred to him that the bike rides were a result of what had happened to Etan. “I just thought it was an awesome thing to do with my dad.”

Last week, after a federal appeals court reversed the conviction of Pedro Hernandez, a former bodega worker who was found guilty in 2017 of kidnapping and killing Etan, the case returned to the spotlight, inspiring a new round of conversations about how to raise children.