National school walkout: U.S. Students protest gun violence
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People supporting gun control attend a hearing by the Senate Judiciary Committee during a hearing about legislative proposals to improve school safety in the wake of the mass shooting at the high school in Parkland, Florida, on Capitol Hill in Washington.
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Columbine High School student Leah Zunder holds a sign during a National School Walkout in Littleton, Colorado.
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Roosevelt High School student organizers Scout Smissen, 17, and Gabe Rosenbloom march with Zach Heffron, 18, of Nathan Hale High School as they march with hundreds of other students to the University of Washington in Seattle, Washington.