NATIONWIDE — Thousands of students are expected to walk out of classrooms nationwide Wednesday in a protest of gun violence and a call for new gun control measures.

The nationwide walkout is happening on the one-month anniversary of the Parkland school shooting that left 17 dead.

From Maine to Hawaii, this movement is expected to be the biggest demonstration yet of the student activism that has emerged in response to last month's massacre.

The walkout was organized by Empower, the youth wing of the Women's March, which brought thousands to Washington D.C. last year.

Students will leave class at 10 a.m. local time for 17 minutes — one minute for each victim in the Florida shooting.

"Our elected officials must do more than tweet thoughts and prayers in response to this violence," the group said on its website.

The American Civil Liberties Union issued advice for students, saying schools can't legally punish them more harshly because of the political nature of their message.

Do I have First Amendment rights in school?

Yes. You do not lose your right to free speech just by walking into school. You have the right to speak out, hand out flyers and petitions, and wear expressive clothing in school — as long as you don’t disrupt the functioning of the school or violate the school’s content-neutral policies. What counts as “disruptive” will vary by context, but a school disagreeing with your position or thinking your speech is controversial or in “bad taste” is not enough to qualify. 

Can my school discipline me for participating?

Yes. Because the law in most places requires students to go to school, schools can discipline you for missing class. But what they can’t do is discipline you more harshly because of the political nature of or the message behind your action. The exact punishment you could face will vary by your state, school district, and school. Find out more by reading the policies of your school and school district.

In Pennsylvania, Wisconsin and Texas, some lawyers said they will provide free legal help to students who are punished.

The ACLU of Georgia's guidance letters to districts said "The United States Supreme Court has long held that students do not 'shed their constitutional rights to freedom of speech or expression at the schoolhouse gate'."

The March for Our Lives rally for school safety is expected to draw hundreds of thousands to the nation's capital on March 24, its organizers said. And another round of school walkouts is planned for April 20, the 19th anniversary of the Columbine High School shooting in Colorado.

The possibility of being suspended "is overwhelming, and I understand that it's scary for a lot of students," said Lian Kleinman, a junior at Pope High. "For me personally this is something I believe in, this is something I will go to the ends of the Earth for."

Other schools sought a middle ground, offering "teach-ins" or group discussions on gun violence and working to keep things safe. Officials at Boston Public Schools said they arranged a day of observance Wednesday with a variety of activities "to provide healthy and safe opportunities for students to express their views, feelings and concerns." Students who don't want to participate could bring a note from a parent to opt out.

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The Associated Press contributed to this report.