KANSAS CITY, Kan. (AP) — A months-long dispute between a Kansas City school district and students alleging free speech violations has escalated into a court battle involving the American Civil Liberties Union.

The ACLU of Kansas asked the U.S. Court for the District of Kansas this week to allow its lawsuit to proceed against the Shawnee Mission School District, the Kansas City Star reported . The response came after the district filed a motion last month asking to dismiss the federal lawsuit filed in May.

The dispute began April 20 when students alleged district officials intervened and stopped them from fully participating in a nationwide walkout protesting gun violence. The 17-minute walkout marked the 17 people who were killed earlier this year at a school shooting in Parkland, Florida.

Shawnee Mission North High School students said district officials required them to speak from an approved script for the walkout and that an associate principal took cameras away from student journalists. Students from Hocker Grove Middle School complained their event was cut short because officials had not approved language about gun control or gun violence.

The lawsuit accuses the district of suppressing students' political speech on campus "merely to avoid controversy."

Former interim Superintendent Kenneth Southwick promised in a public meeting days after the rally that he would take personal responsibility for any attempted censorship of students. Southwick said the district would investigate the complaints and likely host a training session for all school administrators on students' free speech rights.

The ACLU filed the lawsuit after students and parents said they were unsatisfied with the district's response. But the district argued in court documents that school leaders were justified in censoring students because of concern that others might have wrongly assumed their voices reflected the district's position.

"Instead of simply acknowledging their violation of student First Amendment rights, the district appears to be doubling down on the mistakes they've made," ACLU Legal Director Lauren Bonds said Wednesday.

District officials said they support students' rights to self-expression and "will continue to work with staff to ensure that those rights are respected and protected."

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Information from: The Kansas City Star, http://www.kcstar.com