I guarantee that if you just gave each of these kids $10,000 to get on a plane and go back home, they’d all be gone in a week.
Round 'em up and march their asses to the border crossings, Trail of Tears style. Feed them beans and rice and water them... They will be gone in a month at littlecost to the taxpayer... AND THEY WILL NOT WANT TO EVER COME BACK.
Perhaps they will tell their friends not to bother.