The “children” who have been allowed in from northern France were joining relatives already in Britain, the Home Office said.
It insisted all had undergone rigorous interviews and checks on documents to try to prove they were under 18.
Their appearance is also used to see if migrants look as young as they claim. But they are only rejected if they are clearly over 18.
Extensive medical tests, including examining dental records, have been ruled out as too “intrusive”.