Oh, those kids! Those kids in Florida, walking out to protest assault weapons. What difference do they imagine they can make?

Do not count them out.

Student protests have a long, storied, and effective past in the United States. In the late 1960s, they changed the nation’s attitude toward the Vietnam War. And, before that…

In Prince Edward County in the heart of Virginia, 16-year-old Barbara Johns led her fellow students out of the R. R. Moton High School. They protested the separate and very unequal schools provided to members of their race: tarpaper shacks as school additions for them, brick buildings for the whites.

The walkout on April 23, 1951—a lifetime ago—helped to change the course of the segregated south. The students’ suit was joined to the landmark Brown v. Board of Education in which, in 1954, the Supreme Court ruled that separate facilities for different races were inherently unequal.

The drive for civil rights, the one that worked, beg...