Hundreds of thousands of students, teachers, school staffers and their supporters are expected to walk out of their classes today to protest gun violence. Plans for today’s walkout began with an online petition started by 16-year-old Connecticut high school sophomore Lane Murdock, who spoke last month in New York City during another nationwide day of student walkouts.

Lane Murdock: “This is an uphill climb. We have a lot of powerful people against us. And they’re going to want infighting. They’re going to want division. They’re going to want us to look at our differences so they can take us down easier. And we’re not going to let that happen. This is about people—gay, straight, black, white, religious, nonreligious—coming together so their kids don’t have to be afraid to go to school.”

Today’s protest comes on the 19th anniversary of the Columbine High School massacre in Littleton, Colorado, and less than a month after the historic March for Our Lives in Washington, D.C., which saw hundreds of thousands flood the National Mall to demand an end to gun violence.