As Frobisher, Lois and Bridget, seen from behind, start up the stairs together, two other people coming down pass them. In the reverse shot, when they are less than halfway up, the other people have vanished.
Colonel Oduya states that the children stopped at "8.40 GMT". From the paper that Ianto picks up the date is given as "Wednesday September 2009". If this is correct, then the UK is still on B(ritish) S(ummer) T(ime), and "8.40 GMT" doesn't fit with the school run.
During the second takeover of the children, a blond boy in a red school uniform (farthest to the right) briefly glances at the camera when all the other children's eyes are fixed off in the distance. When he notices that he's on camera his eyes quickly dart back to fixed and blank.