The mother of a transgender high school student said her daughter had suffered greatly after being banned from a suburban Chicago girls’ locker room, in the family’s first comments since the US Department of Education found the school district had violated her rights.

The comments were published on the website of the American Civil Liberties Union of Illinois, which is representing the girl in a federal complaint against the Palatine-based Township High School District 211.

The girl filed a grievance with the Department of Education’s civil rights office after being denied unrestricted locker room access. Last week, federal officials found the district violated the student’s rights under Title IX.

The student’s name has not been released during the legal proceedings, and the mother’s name was not published with her roughly 1,000-word essay titled Our Child Is a Girl.

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The mother described the family’s struggle with the daughter’s identity and the effect of not being able to use the girls’ bathroom or locker room or play on a girls’ sports team. It described her being “bullied on a daily basis”.

“There were times she was inconsolable and all we could do was hold her and tell her that we loved her and would continue to advocate on her behalf,” the mother wrote.

District officials have said they made reasonable accommodations for the student. They have said their policy is not in violation of the law and must balance the rights of the student with the privacy rights of the other 12,000-plus students.

“The students in our schools are teenagers, not adults, and one’s gender is not the same as one’s anatomy,” the district said in a statement, according to the Chicago Tribune. “Our responsibility as school administrators is to protect the privacy rights of all our students.”

Settlement negotiations continue with the federal education department and the district, which risks losing up to $6m in federal funding if it can’t reach an agreement with the agency.

The mother wrote that she and her husband once believed “simple anatomy” separated a boy from a girl. But she said after her child called herself a girl at age 4 and wanted to wear girls’ clothing, they questioned their understanding. She said they sought help from medical professionals as well as a church, family, the school and friends.

She wrote that the process has taught them acceptance.

“Through this education process, we learned that gender extends beyond the sex a person is assigned at birth,” she wrote.