The charity's report reveals the trauma children have suffered getting to Europe.
Two attackers were to detonate suicide vests while others were to kill passersby with guns, prosecutors say.
The large fishing boat rocks violently before capsizing, sending migrants tumbling into the sea.
Ankara is unable to fulfil all the EU's conditions for unrestricted travel.
Immigration Minster James Brokenshire proposes new Immigration Bill measures that will allow children to be dispersed across local authorities.
The charity says the EU cannot delegate responsibility to Turkey.
The U.N. found that some of the deported refugees were denied the chance to claim asylum.
The deal means disappointment—or at least an ongoing legal limbo—for the thousands who have been piling into flimsy boats to reach Greece.
Hundreds of migrants marched out of Greece and hiked for hours to get around a border fence and cross into Macedonia, where they were detained.
Turkey has warned that even more Syrian refugees may soon arrive seeking asylum.