DENVER — Colorado officials say a suburban Colorado Springs school district discriminated against a 6-year-old transgender girl by preventing her from using the girls' bathroom, in what advocates described as the first such ruling in the next frontier in civil rights.

Coy Mathis's family raised the issue after school officials at Eagleside Elementary in Fountain said the first-grader could use restrooms in either the teachers' lounge or in the nurse's office, but not the girls' bathroom. Coy's parents feared she would be stigmatized and bullied.

On Monday, the Mathis family and its lawyers celebrated the ruling on the steps of the state capitol. Coy, dressed in a glittering tank top, jeans and pink canvas sneakers, ran around a towering blue spruce tree as her mother spoke to reporters.

"Her future will be better if we get to this place where this is nothing to be ashamed of," Kathryn Mathis said, noting the family hadn't sought a civil rights battle but was happy for the Colorado Division of Civil Rights' ruling.

As the gay rights movement has won mounting legal and electoral victories in recent years, advocates hope the latest decision will lend momentum to the struggles of transgendered people.

"This is by far the high-water mark for cases dealing with the rights of transgendered people to access bathrooms," said the Mathis family's attorney, Michael Silverman of the Transgender Legal Defense & Education Fund. He and other advocates said the case is one of several potentially ground-breaking transgendered civil-rights cases winding their way through the nation's courts.

The Maine Supreme Court is considering the case of a 15-year-old transgendered girl who was forbidden from using her school's girls' bathroom.

Mat Staver of Liberty Counsel, which focuses on religious and family litigation, said transgender cases are "a mockery of civil rights." He said his group got involved defending a department store employee who was disciplined for ordering a person who was obviously male to leave the women's changing room.

"How do you know if someone is really thinking this way or not," Staver said, adding that Coy is too young to decide on such a different identity. "How do you know if someone just wants to go in the restroom and be a peeping Tom?"

Coy was born a triplet with two sisters and identified as a girl before she began attending elementary school in Fountain-Fort Carson School District 8, an area heavy with military personnel near an Army base. Her father, Jeremy, is an ex-Marine.

At 5 months, she took a pink blanket meant for her sister Lily. Later, she showed little interest in toy cars and boy clothes with pictures of sports, monsters and dinosaurs on them. She refused to leave the house if she had to wear boy clothes. After her parents accepted her identity, they said, Coy come out of her shell.

Coy was diagnosed with "gender identity disorder" — a designation the American Psychiatric Association removed last year from its list of mental ailments. The removal reflected the growing medical consensus that identification as another gender cannot be changed.

The Mathises said they feared the district's decision would stigmatize Coy, who was reduced to tears when her teacher briefly put her in the boys' line. When she came home, according to legal records, she cried to her parents: "Not even my teachers know I'm a girl!" When Coy rose to first grade, the district forbade her from using the girls' restroom.

The Mathises filed their complaint in February. The civil rights board's director, Steven Chavez, found in a legal determination issued June 18 that the district's solution of letting Coy use staff bathrooms smacked of "separate but equal" and clearly violated her rights.

Since they filed their complaint, the Mathises have moved to the Denver suburb of Aurora because of health problems suffered by another daughter. They said they hope the ruling will make it easier for Coy to start at a new school without worrying about which bathroom she can use.

Fountain-Fort Carson School District 8 declined to discuss the case Monday. The district, however, can seek arbitration or a public trial, said Cory Everett-Lozano, a spokeswoman with the Colorado Department of Regulatory Agencies.

Silverman said transgendered civil rights are largely where gay rights were in the 1980s. He said progress in gay rights has made it easier for transgendered people to dare to fight in court.

Coy, he said, is such an example. Her parents grew up during a more tolerant era for sexual rights and recognized that they should not try to force her to be a boy. "That has allowed children like Coy to make their voices heard," Silverman said.

Last year, Vice President Joe Biden called transgendered rights "the civil rights issue of our time." Sixteen states, including Colorado, and the District of Columbia expressly outlaw discrimination against transgendered people. In 2011, the 11th Circuit Court of Appeals in Atlanta overturned the firing of a Georgia state legislative employee who was dismissed after telling her boss she was about to undergo sex change surgery.

"We're at a crisis point" on transgendered rights, said M. Dru Levasseur, director of the Transgender Rights Project Director at the Lambda Legal Defense Fund, adding that 44 percent of hate-motivated murders in 2010 were of transgendered women. "Transgendered people don't always fit in binary boxes so there has been more difficulty in social acceptance" compared to gay people.

Peter Sprigg, a senior fellow at the Family Research Council in Washington, D.C., said there is clearly "a new social movement," which his group opposes, to protect the rights of transgendered people in court and state legislatures.

"In many places, the activists have already succeeded in having sexual orientation" protected, Sprigg said. But expanding those rights to transgendered people may be tougher because that population's behavior is more overtly different, he said.

"Sexual orientation is largely invisible," Sprigg said. "In this case, you're dealing with something that's manifest visibly."