After watching the movie "The Help", she started using a quote from the movie. Every day she would tell her preschoolers, "You are kind. You are smart. You are important." She said their faces just lit up whenever she told them this.
If she heard them say something negative about themselves, she would respond by repeating "You are kind. You are smart. You are important." She found that reminding them of this brought out the best in their behavior.
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