Alone and Exploited, Migrant Children Work Brutal Jobs Across the U.S.

It was almost midnight in Grand Rapids, Mich., but inside the factory everything was bright. A conveyor belt carried bags of Cheerios past a cluster of young workers. One was 15-year-old Carolina Yoc, who came to the United States on her own last year to live with a relative she had never met.

About every 10 seconds, she stuffed a sealed plastic bag of cereal into a passing yellow carton. It could be dangerous work, with fast-moving pulleys and gears that had torn off fingers and ripped open a woman’s scalp.

The factory was full of underage workers like Carolina, who had crossed the Southern border by themselves and were now spending late hours bent over hazardous machinery, in violation of...