Facial Expression
Facial Expression is a movement of the face muscles that shows what a person is feeling or thinking.
Think of it this way
A tray holds three lumps of dough, each pressed into a different shape. One is flat, one is dented down, and one has its edges pushed up. Each shape tells you how the dough was handled. Face muscles work the same way: they pull skin into shapes that show a feeling.
Explaining facial expression by grade level
Look at someone who is smiling. Their mouth turns up and their eyes get small. Now think of someone who is scared. Their eyes go wide and their mouth drops open. Each feeling makes the face move in a different way.