This story may not be appropriate for younger readers. First-grader Coy Mathis from Fountain, Colo., is not allowed to use the girls restroom at her elementary school because she is transgender.

The 6-year-old has been using the school's girls restroom but was banned from doing so in December 2012. The school's administrators informed Coy's parents that Coy would have to use the boys or the staff restrooms instead.

Coy Mathis was born a male triplet, but has lived like a girl since she was 18 months old. Coy plays with Barbies, while her two brothers play with dinosaurs and trucks. Her parents say at age 4, Coy was telling her mother that something was wrong with her body. Coy has considered herself as a girl since 18 months old -- even her passport and state-issued identification recognize her as female.

According to Radar.com, the attorney for the school district says the school’s decision “took into account not only Coy but other students in the building, their parents, and the future impact a boy with male genitals using a girls bathroom would have as Coy grew older.”

The letter also made reference that the presence of Mathis' in the women's bathroom would be “psychologically damaging” later in life, and so the school chose to address the matter now.

The Mathis family has filed a complaint with the Colorado Civil Rights Division, which is the first of its kind to test the state's Anti-Discrimination Act, which does include protection based on gender identity.

Mathis’ parents are homeschooling her until the case is resolved.