When Jamie is playing "War" with Mrs. Frankweiler, with the camera on him, he plays his last card, he loses it, and his hands are empty. She takes her winning, and her hands are empty also. An instant later, after the cut, with the camera on her, she has cards in her hand and plays one more card on "his" card - a card that can not be there.
When the children get off the school bus, and head through downtown to the train for NYC, a group of 20 or 30 onlookers, especially children on bikes, is caught across the street observing the filming.
After the kids get off the school bus and are walking down the street, a clear reflection of the boom microphone is briefly visible in one of the store windows.
When Mrs. Frankweiler is on the phone with the information operator, she says she does not know the first names of the Kincaids. However, she should have known as she earlier stated she had read about the missing children for days in the newspaper and it seen carrying a paper minutes before.