VIDEO : George Clooney, Paul McCartney and Other Celebrities Join March for Our Lives

Several celebrities showed their support for the student organizers behind March for Our Lives. In Washington D.C., Miley Cyrus, Ariana Grande and Common were among the performers. At a rally in Los Angeles, comedian Amy Schumer pleaded for lawmakers to protect children from gun violence. Schumer has been an outspoken gun-control advocate since a shooting at a screening of her film "Trainwreck." George and Amal Clooney donated $500,000 to the event. Singer Paul McCartney marched in New York City. He spoke of losing his best friend John Lennon.