Coy Mathis, born a male triplet, has behaved like a girl since she was 18 months old. When her brother Max was consumed with dinosaurs, she was playing with Barbie dolls. By 4, she was telling her mother that something was wrong with her body. Since being enrolled at Eagle Elementary School in Fountain, Colo., the 6-year-old has presented as female and wearing girls' clothing. Her classmates and teachers have used female pronouns to refer to her, and she has used the girls' bathrooms.