Coy Mathis is 6 years old and transgender. She has the body parts of a boy, but the rest of her, she says, is all girl.
Her parents noticed the contradiction when Coy was about 18 months old. Small things, like Coy liking anything pink and sparkly, added up. Then, as Coy got older, she came right out and said "I'm a girl."
From then on, she has lived as a girl, and people have treated her like a girl -- including her school, where she used the girl's bathroom.
Then, after a year attending the school, administrators said Coy could no longer use the girl's bathroom. They said she could use the boy's bathroom, a staff bathroom, or a bathroom in the nurse's office.
Coy's family says that's discrimination--or as Coy puts it--"mean." They have filed an official complaint with the state.
Colorado has a law that bans discrimination against people who are transgender, but the law has never been tested with regard to school bathrooms.
The school says its decision takes into account not only Coy, but also other students and their parents, and it says it's not violating the law.
Coy's parents say kids should be taught that people's differences are okay and should be embraced--not stigmatized.
"Coy deserves to be treated like every other girl," her mother says. "She's a girl and that's who she says she is. That's who she's always been and that's how we're going to allow her to be."
The state of Maine has a similar anti-discrimination law, but a court there ruled it was legal for a school to deny a transgender student access to a girls' bathroom.
Illinois also has a law protecting people who are transgender from discrimination.