The argument that young protesters can’t engineer policy change isn't a new one. But those still making the argument must not be familiar with the United States' storied tradition of youth activism.

Students from more than 2,800 schools left their classrooms Wednesday to participate in National Walkout Day, a protest in which they demanded that lawmakers consider stricter gun-control laws in the wake of the Feb. 14 school massacre in Parkland, Fla.

The idea behind the protest originated with EMPOWER, the youth branch of the Women's March, which drew millions of protesters around the world the day after President Trump was inaugurated last year.

It is not clear whether these student protests will lead to significant policy change. But it is clear that past protests have been effective at attracting the attention of lawmakers.

Here are a few examples of youth protests that have brought about policy changes:

Children’s Crusade

In May 1963, thousands of children gathered at the 16th Street Baptist Church in Birmingham, Ala., and then dispersed in groups to peacefully protest segregation in the city. The protesters had intended to talk to the mayor about segregation, but they were met with hostility. Hundreds were arrested, and police sprayed the children with powerful water hoses, beat them with batons and threatened them with police dogs. This protest was one of many during the civil rights movement that led lawmakers to understand the importance of desegregating schools and other public spaces.

Newsboys' Strike of 1899

The youth-led protest was rooted in child-labor laws. Newspaper delivery boys wanted newspaper publishers Joseph Pulitzer and William Randolph Hearst to improve compensation for the children selling their products. Rallies, protests and support from adults led to success and, eventually, helped reform child-labor laws.

March for Life

Thousands of antiabortion activists descended on the Mall in January, as they do annually on the anniversary of the Supreme Court decision in Roe v. Wade, which legalized abortion. The gathering typically draws busloads of Catholic school students, evangelical Christian teenagers and young people affiliated with Students for Life who encourage lawmakers to back policies that make abortion illegal. This year’s event was attended by Vice President Pence and featured a message from President Trump that he delivered from the White House. It was the first such presidential broadcast at the event; Ronald Reagan and George W. Bush addressed the march by telephone. After declaring his commitment to the community, Trump pledged to support policies that make abortions more difficult to obtain.

Ferguson

After Michael Brown, an unarmed black teenager, was fatally shot in August 2014 by a white police officer in Ferguson, Mo., students protested in the St. Louis suburb for weeks, drawing attention to police violence against people of color nationwide. The incident led President Barack Obama to call for a White House task force on policing to improve reporting of police-involved shootings and to improve police training.

Those who participated in the walkout and march to the U.S. Capitol on Wednesday heard from lawmakers such as Sen. Bernie Sanders (I-Vt.) and House Minority Leader Nancy Pelosi (D-Calif.), who voiced support for the efforts.

But conservatives suggested that Democrats are using these students as a political tool to push for anti-gun legislation.

“They've been putting forward this message that if you disagree with them on gun control, then this means you don't care enough about the kids, and now they are activating these kids, and putting them out on the front lines, and putting them in photo ops, so that they can essentially use them as political human shields,” conservative radio host Ben Shapiro told Fox News Channel on Wednesday.

Given that Shapiro and other conservatives have advised students on the right to stage counter-protests, it appears as though both sides see the value in championing young people to voice their political opinions.

And if history is any indicator, the walkout could launch the careers of future policymakers. Just ask Rep. John Lewis (D-Ga.), who first became involved in protests as a student in Nashville.