A poster created by several students to protest grand jury decisions not to indict two police officers who killed unarmed black men could soon be back on the walls at Lewiston High School.

“Based on what I know, I don’t see any reason it should not be posted,” Lewiston Superintendent Bill Webster said Wednesday.

Webster plans to meet Thursday with the four girls who put up the poster to discuss it and tell them his decision.

The girls created the poster because they wanted to get involved in some way with the nationwide protests over the killings. They had abandoned their original idea, to walk out of classes to join the protests last week, after school officials told them there could be “unintended consequences” if they walked out. The four said they assumed that meant they could be suspended, and went along with Principal Linda MacKenzie’s suggestion to make a poster instead.

They put up the poster Friday, but Chandler Clothier, the student who designed it, said she was called to the principal’s office on Monday. MacKenzie told her that she failed to get prior approval for the poster, and that she needed to change the title “#blacklivesmatter” to “all lives matter” or take the poster down, Clothier said.

“#blacklivesmatter” is the Twitter hashtag that has been commonly used as part of the nationwide conversation over racial justice and the incidents in Ferguson, Missouri, and New York City, in which unarmed black men died at the hands of police officers. Grand juries in both cases declined to indict the officers, sparking protests in many cities, including Portland.

The girls removed the poster, but said they believed their free speech rights were being violated, particularly because the principal demanded a change in wording.

They were probably right, said Zachary Heiden, the legal director of the American Civil Liberties Union of Maine, which was aware of the incident but is not involved. Heiden said the organization would give the students legal help if asked.

In a previous ruling over student protests of the Vietnam War, the U.S. Supreme Court said that “students don’t check their constitutional rights at the schoolhouse gate,” Heiden said.

He said schools control their walls, but only to the extent that they allow free expression that’s not substantially disruptive to learning.

School officials “aren’t supposed to make decisions based on the message conveyed,” Heiden said. “That raises problems from a First Amendment standpoint.”

Webster said he reviewed the district’s 603-page policy manual Tuesday and realized that as superintendent, he, not the school principal, is supposed to approve posters and material to be distributed in schools. He said the policy bars material that is “hate” literature; material that creates hostility, disorder or violence; commercial, political or pornographic material; and libelous material.

“At this point, I’m not aware of anything on the poster that would cause me to say it should not be posted, although I haven’t seen it yet,” Webster said. He said he understands that the subject of the poster almost “requires that there be a #blacklivesmatter” hashtag because it has been so commonly used on Twitter to refer to the protests.

MacKenzie did not respond to several messages Wednesday. In an email response to questions Tuesday, she wrote that the girls had failed to get prior approval for the poster.

Lewiston High School’s student body is about 25 percent minority students, Webster said, and many of them are children of immigrants who settled in Lewiston after fleeing violence in Somalia.

Webster believes the school has done a good job integrating what, for Maine, is an unusually large number of minority students.

The students said that’s why it’s important for the school to discuss racial issues.

“It’s an important step for Lewiston High School students’ voices to be heard,” Clothier said.

She said students agreed Wednesday to put the poster on a civil rights bulletin board in the school, once it has been cleared by Webster. Although the bulletin board is in a less prominent place – the poster was originally next to an entrance to the cafeteria – Clothier said it still will be noticed. The new location also will allow other students to post information about civil rights issues, she said.

Muna Mohamed, the senior class president and one of the girls who created the poster, said the placard – and the fight over whether the students could put it up – already has had an effect at school. Her mentoring group discussed the issue of students’ civil rights Wednesday, and other students told her it was a topic of discussion in their advisory groups as well.

“It’s definitely sparked a conversation,” she said. “That needs to happen.”

Mohamed said she hasn’t heard any negative reaction to the poster and its message, but she’s OK with that too, if it comes.

“The whole thing we wanted was for this conversation to happen,” she said. “Probably some people disagree, but that’s needed in a conversation.”