(CNN) -- Just like she did during the first half of the school year, first grader Coy Mathis wants to use the girls' restroom at her Colorado elementary school. But school officials won't let her.
The reason? Coy is transgendered, born with male sex organs but a child who identifies herself as female.
She has dressed as a girl for most of last year. And her passport and state-issued identification recognize her as female.
In December, the Fountain-Fort Carson School District informed Coy's parents that Coy would be barred from using the girls' restrooms at Eagleside Elementary in Fountain after winter break.
She could instead use the boys' bathroom, gender-neutral faculty bathrooms or the nurse's bathroom, the district said.
In making the decision, the district "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," attorney W. Kelly Dude said.
"However, I'm certain you can appreciate that as Coy grows older and his male genitals develop along with the rest of his body, at least some parents and students are likely to become uncomfortable with his continued use of the girls' restroom."
Coy's parents see it differently.
By forcing Coy to use a different bathroom than all the other girls, the school is "targeting her for stigma, bullying and harassment," Michael Silverman, one of Coy's lawyers and the executive director of the Transgender Legal Defense & Education Fund, said.
"Coy's school has the opportunity to turn this around and teach Coy's classmates a valuable lesson about friendship, respect and basic fairness."
On Wednesday, Coy's parents will announce that they will file a complaint with the Colorado Civil Rights Division.