(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.
The issue of transgender identity is somewhat new, and policies vary in school districts around the country.
In New York, for example, the law says students can't be discriminated on the basis of their gender identity.
In Maine, on the other hand, a court ruled in November that a school district did not violate a transgender student's rights when she was told she couldn't use the girl's restroom.
Dude has said there are no Colorado cases that require public schools to permit transgender students to use restrooms of the gender with which they identify.
He added that the district adheres to the Colorado Anti-Discrimination Act because "Coy attends class as all other students, is permitted to wear girls' clothes, and is referred to as the parents have requested."
She also has easy access to bathrooms other than the girls' restroom, Dude said..
Coy's case will be the first to challenge such a restriction under the state's anti-discrimination act, the Transgender Legal Defense & Education Fund said.
For now, the first-grader is being homeschooled.
-- CNN's Cristy Lenz contributed to this report.
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