These children are not intersex -- they do not have a physical disorder or malformation of their sexual organs. The gender issue exists in the brain, though experts do not agree on whether it's psychologically or physiologically based.
Many transgender people report feeling discomfort with their gender as early as they can remember.
Gender identity is often confused with sexual orientation. The difference is that "gender identity is who you are, and sexual orientation is who you want to have sex with," said Dr. Johanna Olson, a professor of clinical pediatrics at the University of Southern California, who treats transgender children.
Children around age 3 are probably not interested in sexual orientation, she said. But experts say some children who look like they will be transgender in early childhood turn out to be gay, lesbian or bisexual.
Differences in schools
School policies toward transgender students vary across the United States.
In New York, for example, the law says students can't be discriminated against on the basis of their gender identity.
But in Maine, 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 girls' bathroom.
Dude, the Colorado school district's attorney, has said there is nothing in that state requiring public schools to permit transgender students to use restrooms intended for the gender with which they identify.
At the time, he argued that the Fountain-Fort Carson School District adheres to the Colorado Anti-Discrimination Act in all respects: "Coy attends class as all other students, is permitted to wear girls' clothes and is referred to as the parents have requested."
On Monday, Silverman underscored what he described as the unfairness of Coy's situation.
"By denying Coy the right to use the little girls restroom like all the other little girls at school it had created an environment that was hostile, discriminatory and unsafe. Coy was treated in what was referred to as an exceptional way, which limited her educational opportunities. In the end, we've been saying from the start, that Coy wants the same dignity, respect and opportunity, and deserves that, as every other student in Colorado. The state of Colorado has now said that's exactly what she deserves," Silverman said.