When Andy tells the story of the American Revolution, a calendar with a picture of geese in flight is on the wall behind him. When he's done, there is instead a photograph of what looks like an airplane in a hangar behind him, with the calendar moved farther along on the wall.
Miss Crump asks her class to raise their hands if they had not done their history homework. Looking from the front of the classroom, only two boys, Opie and Howie behind him, initially raise their hands. However, when the shot is a close-up on Opie and those immediately around him, Johnny Paul, to Opie's left, also has his hand up although he previously did not raise his hand.