The mother of a transgender teen who was on the swim team at Coon Rapids High School is suing the Anoka-Hennepin School District — accusing the state's largest school system of discrimination for not allowing him to use the boys' locker room.

The lawsuit, filed Monday in Anoka County District Court, argues that Anoka-Hennepin school leaders violated the student's constitutional rights, as well as the Minnesota Human Rights Act.

David McKinney, an attorney for the American Civil Liberties Union's (ACLU) Minnesota chapter, said the Anoka-Hennepin school board singled out the student, segregated him from his peers and forced him to use a separate changing room that wasn't being used by any other students.

"This degrading treatment made him feel unwelcomed and alone," McKinney said during a news conference Monday at the St. Paul office of Gender Justice, which joined the ACLU in announcing the lawsuit. "That kind of mistreatment and the exclusion the teen boy has experienced is unacceptable and needs to stop now."

The parent of the transgender teen said her son used the boys' locker room for months before the school board took action. She said she repeatedly asked the board to use Minneapolis and St. Paul Public School Districts' gender inclusion policies as a model. Anoka-Hennepin's decision, she said, robbed her child of a normal high school experience and "altered the course of his life." The student no longer attends school in the district.

"I didn't choose this battle, the school board chose us," she said. "They used their power and went out of their way to create a problem where there wasn't a problem to begin with."

In an e-mailed statement, Anoka-Hennepin said the use of restrooms and locker rooms are determined on a case-by-case basis. The district said its plans to accommodate transgender and nonconforming students are made in consultation with school building administrators, Title IX coordinator and district superintendent. Its policy and practices are consistent with guidance from national and local School Boards Associations, which follow state and federal law, it said.

"Anoka-Hennepin Schools is committed to providing a safe and respectful learning environment and to providing an education that supports all students and families, including transgender and gender nonconforming students," the statement said.

In the court document, the mother and teen are referred to only by the initials "J.H." and "N.H." The attorney said they are using only the family's initials because of hateful threats they have received.

Between 2010 and 2012, the Anoka-Hennepin district attracted national attention after a rash of student suicides occurred and then a lawsuit was filed by a group of students, who alleged that the district was not protecting them from harassment, and allowed uncontrolled bullying and created unequal access to education. The Department of Justice then placed the district under a five-year consent decree, which expired in March 2017.

Christy Hall, a senior staff attorney at Gender Justice, a St. Paul nonprofit legal and advocacy group, said the district was in a monitoring period when it discriminated against the student.

"It's time once and for all that Anoka-Hennepin and all school districts across Minnesota adopt policies and practices that truly ensure a safe and equitable environment for all students, including transgender, gender nonconforming and gender diverse students," Hall said at the news conference.

In February 2016, the school board barred the student from using the boys' locker room, according to the suit. The board later reversed its decision, saying that the teen could use the boys' changing facility until the end of the swim season, the complaint said. The boy's attorneys said the discrimination caused the student significant emotional distress that even led to hospitalization.

Nearly 3 percent of Minnesota's students identify as transgender or gender nonconforming, according to Megan Peterson, Gender Justice's executive director. School districts are still wrestling with how to best accommodate them. Both attorneys at Gender Justice and ACLU argue that the Anoka-Hennepin policy failed to follow guidance about the equal treatment of transgender students from the department.