A group of high school students from Lewiston, Maine is speaking out after school officials impeded their attempts to show solidarity for the growing racial justice movement in the U.S., in a move which they say infringes on their First Amendment rights.

The Lewiston High School students had initially planned to join a nationwide day of walk-outs from schools and places of work to protest police brutality and racial profiling after the recent deaths of Michael Brown, Eric Garner, and other black men and women who were killed by police. But the school administration dissuaded them from taking part in the protest, warning that the action could lead to "unintended consequences," such as suspensions, the Portland, Maine Press Herald reported on Wednesday.

Muna Mohamed, senior class president and one of the student leaders organizing the protest, said the administration advised the group to find another way to express themselves, like hanging a poster.

So they did just that—creating a banner that read "#BlackLivesMatter" and was decorated with quotes that have become symbolic of the movement, including "I can't breathe," Garner's final words.

But shortly after the poster was hung, Principal Linda MacKenzie told them to take it down.

"They keep saying they want students to raise their voices, but they want to define the students’ voices, and I feel that’s unfair," Chandler Clothier, a junior who helped design the poster, told the Press Herald.

School officials said the poster was taken down because the group did not obtain permission to hang it up, as is required, but the students told the Press Herald that that policy is often ignored.

But MacKenzie told the Press Herald that she had not seen the poster.

Senior Kalgaal Issa, who helped create the poster, told the Press Herald that Lewiston High School has largely ignored the recent events that have galvanized people across the country to protest police violence and racism.

"There should be more awareness about it," Issa said. "It’s like this really didn’t happen. That’s unbelievable."

Superintendent Bill Webster said the issue was simply obtaining permission from officials, but reiterated on Wednesday that he would review the poster and determine whether it could be displayed.

"I don't know of any reason why it shouldn't be approved, but I have yet to see it," Webster told the Lewiston-Auburn Sun Journal. "It's been a few years since I've dealt with a poster of a political issue. I look forward to meeting with the students."