What happens to children who are caught crossing into the US?
Unaccompanied children who are caught crossing into the US are supposed to stay in the custody of Border Patrol agents for no more than 72 hours. During that time, they're screened by a Border Patrol officer.
Children coming from Mexico have to prove to the Border Patrol officer that they fear persecution or trafficking in order to stay. Otherwise, they're returned. (It's believed that President Obama plans to ask Congress to extend this to Central American children as well.)
Children who pass the Border Patrol screening, or aren't subjected to it, are sent into the custody of the Office of Refugee Resettlement — part of the Department of Health and Human Services.
Because the government is so overwhelmed by the current influx, many of these children are being held in Border Patrol custody for more than 72 hours, or being held in intermediate detention centers — some of which are makeshift spaces on military bases.
Once the Office of Refugee Resettlement receives a child, it's responsible for keeping the child in an HHS facility while it finds a relative or family friend who can take the child on. (The current crunch has made it difficult for HHS to screen relatives appropriately.) If no relative can be found, the child is placed in long-term foster care.
Meanwhile, the child's immigration case is being processed. In some cases, an asylum officer evaluates a child's claim for asylum; in other cases, the child goes through immigration court, where they might receive asylum or request Special Immigrant Juvenile Status (for children who can't be reunited with their families because of "abuse, negligence or neglect").vox.com