When Dusty hands her grandfather the microphone to pray at the rodeo, the shot from behind shows her standing with her hat still on. When the shot cuts to in front of her, her hat is off and she is fixing her hair.
When Dusty is first introduced to the class, one of the students makes a comment, to which Mrs. Preston responds to try to act their age and not their I.Q. as a way of telling them to "grow up." The correct phrase is to act their age and not their shoe size, as their shoe size is usually a lower number than their physical age while, in this case, their IQ would be much higher than their age. In essence, she was telling the student to act less mature, not more mature.