It was supposed to be a routine checkup for five-year-old Thomas Curtis of Kyle, who was about to start kindergarten. But what his family was told was devastating – that Travis was fine except for nearly total hearing loss that, in the words of his grandfather Thomas Gunn, “probably couldn’t be fixed with a hearing aid.”

“We just assumed his lack of attention when being talked to by teachers and family was a normal five-year-old’s rebuke of authority,” Gu...