The mother of the trans girl at the center of the controversy in Palatine, IL has posted an essay by the title name at the ACLU-IL website.

The ACLU of Illinois is representing the family in their dealings with the school district. The mother writing the essay says that her daughter's friends call her "the most famous anonymous student." Her daughter is "Student A" in the legal proceedings.

[O]ur daughter is “Student A” at the center of the recent controversy over whether a girl who is transgender should be permitted to use the girls’ locker room. The Department of Education’s Office of Civil Rights says yes. Our school district — Township District 211 — insists that students “of the opposite sex” should not be permitted in the girls’ locker room.

For the record, we agree with District Superintendent Daniel Cates about not permitting students of the opposite sex in the locker room. But the inconvenient fact for Mr. Cates and his supporters is that our daughter is not “of the opposite sex.”

She is a girl.

The district wrongly assumes what many who are not educated about the issue assume: That what makes a girl a girl and a boy a boy is simple anatomy. We believed this, until our daughter came along. Despite early signs — from as young as four, when she declared herself a girl, to the fact that she had mostly girlfriends growing up, played with dolls, begged to wear girls’ clothes, insisted on wearing a Hannah Montana wig while she danced around the living room, and was heavily distraught over the male characteristics of her body — we were still shocked and ill-prepared when, at the end of seventh grade, our daughter again told us that she was a girl and had to live openly as one.

There is an interesting history of exactly what as thought to distinguish men from women throughout the ages. Sarah Richardson's Sex Itself is a good exploration of that.

In the 16th century, scientists believed sexual differences were down to the blood. By the 18th century it was the pelvis. In the 19th century the main determinant was the skull...which soon led to the brain:

[W]hen scientists discovered that female brains were, on average, smaller than male brains, they attributed the supposed lower intelligence of women to their smaller brains. Since it was scientifically proven and congruent with existing stereotypes, there was little critical examination of the core claim: that larger brains lead to greater intelligence. Further research has shown that there is not a link between brain size and intelligence, and that women are not less intelligent than men.

--Fisk, Sex and the human genome

In the 20th century sex differences were first attributed to hormones, before moving on to the human genome.

While many previous scientific claims to explain sex differences were proven false, this does not imply that women and men have no meaningful genetic differences. But to produce good science, Richardson argued that scientists must critically examine their results while keeping in mind the failures of earlier work on sexual differences. In particular, she contends that by assuming an X- and Y- chromosome sex binary, we neglect the variation that occurs within each sex as well the overlap between the sexes.

According to Richardson, this could create, “bad science that could harm women’s and men’s health.” In an age of increasingly personalized medicine, doctors might prescribe treatment based on an individual’s sex as opposed to their individual traits. For instance, while men generally weigh more than women, there is immense variation: there are women who weigh more than most men, and men who weigh less than most women. For this reason, making dosing decisions based on sex category, as opposed to an individual’s weight, would be disastrous: some individuals would get too much of a drug, while others would get too little. Either way, the results could be life threatening.

--Fisk

On an ethical level, Richardson argued that focusing on difference is also harmful. It leads us to overstate the difference between women and men, the end result being a reinforcement of stereotypes (e.g. men are aggressive, women are emotional) and ignorance of the great variation and overlap between men and women.

I do think that these claims cause harm in terms of our conception of males and females as species beings who have biologically conscribed sex and gender roles.

We have an opportunity for critical intervention, and we urgently need to have an open methodological, conceptual, and also at once ethical debate about conceptualizing sex differences in the human genome.

There are good methodological, empirical, and ethical reasons to look at sex differences in the genome in new ways, and this is the interdisciplinary conversation I hope to open.

--Richardson

This is a difficult concept to grasp. However, just because something is difficult to understand, does not mean we should mock it or deny its existence. When we were struggling to understand, we sought out medical professionals and support groups. Through this education process, we learned that gender extends beyond the sex a person is assigned at birth. We learned that scientific evidence has determined that gender is also determined by the brain’s anatomy, which is why the sexual characteristics assigned to many at birth are incongruent with their true gender identity. We also learned that one’s gender identity is different from one’s sexual orientation.

Most importantly, we learned acceptance.

We then tried to work with our daughter’s educators, our church, and family and friends to mitigate the risk that she would be one of the at least 20 transgender individuals who were brutally murdered this year or one of the more than fifty percent of transgender youth who attempt suicide by the age of 20. We were cautiously optimistic when many of our family and friends expressed support. However, we faced roadblocks early on with the school system.

--Mother of Student A

The fact that neighboring school districts have managed to grant transgender youth access to the locker rooms which correspond with their gender identity without any issues only serves to highlight that District 211’s stated concerns are mere subterfuge for discrimination. The only real fear is that which my daughter faces now and probably will for the rest of her life — fear that she will never be truly accepted by society, fear that she will never get married and have a family, and, most concerning, fear that she will be harmed by people who are threatened by her very existence.

Some of the opinions and comments on this case have been hurtful and difficult to read; still, we are pleased that the issue is in the public discourse. We are hopeful that those with open minds and hearts will come to a place of acceptance. And we are thankful for the courageous voices of those who came before us and those who stand beside us in this journey for justice. And while our daughter will continue to remain anonymous for now, she is well-represented by the thousands of transgender youth who are fighting for the right to live as their true authentic selves.

--Anonymous Mom