Smuggling fees will escalate. When that happens, smugglers often collect half in the home country and require children to work off the other half as indentured servants. Experts expect to see more cases like the one in 2014, when federal agents rescued eight Guatemalan teenagers from a trailer park in Ohio, where they’d been held captive by smugglers and forced to work at an egg farm.

Children will be afraid to admit they have parents here, as they were in the late 1990s and early 2000s, when the government often told parents to retrieve apprehended children, only to deport the whole family when they showed up. As a result children languished in detention centers. Eighteen years ago, I spent a week in a jail in Liberty, Tex., where unaccompanied children who had been kept there for months had tried to slit their wrists or hang themselves.

Finally, advocates worry that Central American children will tell Border Patrol agents that they are Mexican, so they won’t be deported so far away. This was common a decade ago, and resulted in Central American children being preyed upon in lawless, cartel-controlled Mexican border towns. Today, 18,000 Central Americans are still kidnapped and ransomed each year while migrating through Mexico. Children whose families cannot pay are enslaved, raped, killed. Each year, a caravan of Central American mothers walk through Mexico, searching for missing children.

Why would immigrants — parents and children — take these risks? El Salvador, Guatemala and Honduras have among the highest homicide rates in the world. Boys are forced to join gangs; girls are forced to sleep with gangsters. The proof children are fleeing real danger: 73 percent of unaccompanied minors who go to immigration court with a lawyer win the right to stay here legally.

Kendra and Roberto’s mother, Doris Cruz Garcia, 34, fled El Salvador in 2013 after repeated beatings and death threats by Kendra’s father, a gang member. When Ms. Cruz became pregnant with Kendra, he kicked and punched her, trying to abort the baby. Ms. Cruz curled her body into a ball to protect her daughter, who was born two months early, weighing 3.5 pounds.

Ms. Cruz moved with the children constantly to hide from her ex. When Kendra was 3, he broke into the place where they were staying and attacked Ms. Cruz. When she came to the next day, she was covered in blood. Her ex had said he would kill her, that she would end up in a trash bag. She now believed him. She had to escape.

She had just enough money to get herself to the United States, so she planned to save up and send for Kendra and Roberto when she had the money. She thought they would be safe with her brother. But her brother was murdered a year later, probably by members of her ex’s gang.