When Mrs. McGuire checks Matt's temperature she takes the thermometer out of his mouth and leaves the room on the phone. But in the next shot we see Matt, only now he has the thermometer and is using a flashlight in order to heat it up.
When Matt is faking being ill to get out of school, Mrs. McGuire discovers he is not really ill. At one point through the day she suggests to Matt that they spin some yarn and she picks up a basket full of it. Yet in the next shot the position of the balls of yarn in the basket has completely changed.
Miranda wears an outfit for picture day accompanied with two little fluffy hair-balls in the left side of her hair. However when Miranda spots Kate wearing the same outfit as her, you can tell the shot is flipped because the hair-balls have swapped sides.
While the dark blue yarn is in a skein and thus ready to be wound (in other words, put into a ball), the light blue, pink, and cream yarns are already in ball form (a long ball, for the light blue). Even the dark blue is partially wound and Jo unwinds that onto Matt's hands. However, this is obviously a make-work exercise designed to annoy Matt for playing sick, so Jo may have done it on purpose.