E. Dianne Braddock, sister of Carole Robertson, one of the four girls killed in the 16th Street Birmingham, Ala., church bombing in 1963, speaks to a group of middle-school students about the civil rights movement. (Nikki Kahn/The Washington Post)

The students at Kenmoor Middle School in Prince George’s County were about the same age as the young girl in the photo, taken more than 50 years ago.

The picture, along with books and other mementos, sat on a table near E. Dianne Braddock, 69, as she spoke about growing up in the segregated South. But the girl in the photo, dressed in her Sunday best with white-rimmed glasses, a yellow hat and long, white gloves, was not Braddock.

It was Carole Robertson, Braddock’s younger sister, who was one of four girls killed on Sept. 15, 1963, when a bomb ripped through the 16th Street Baptist Church in Birmingham, Ala. Twenty-two other churchgoers were injured.

The girls’ deaths, at the hands of those fighting the end of racial segregation, was a pivotal moment in the nation’s civil rights movement. It galvanized the country and increased support for the cause, which led to the passage of the Civil Rights Act of 1964.

Last year, Robertson, Addie Mae Collins and Cynthia Wesley, who were 14 at the time, and Denise McNair, 11, were posthumously awarded the Congressional Gold Medal, the nation’s highest civilian honor.

As Braddock spoke to the eighth-grade students at the Landover middle school this week, a bronze replica of the medal given to her family was nearby on a table. She said that when she met President Obama for the signing of the bill to recognize the girls, he told the families: “Thank you on behalf of a grateful nation.”

The students — who watched the Oscar-nominated Spike Lee documentary “4 Little Girls” — sat in rapt attention as Braddock, a retired county principal, talked about how her brother couldn’t hang out with his friends at night because their parents worried that he might get stopped by the “mean white people” and “no one would ever see [him] again.”

She shared how her mother, Alpha Robertson, a teacher, couldn’t try on clothes at the department store downtown or eat at the store’s lunch counter.

And then she talked about how Carole Robertson and her friends were in the church restroom when a bomb thrown from a passing car exploded. One survivor lost her eye in the blast and still has charred glass in her body, she told the students. Some of them gasped.

“I didn’t know what all these people went through during that time,” said Lola Fatinikun, 14, of Landover. “It was sad and unfair.”

Melvina Barton, the media specialist who organized the presentation, said she wanted the students to not only explore the nation’s past but to also think about the progress that has been made and how much more needs to be done. That message resonated with Wesley Carter, 14, of Bowie: “We need to know our history and how privileged we are.”

When Braddock asked the students about the strides made by African Americans, they said there have been gains but not enough.

For example, Caleb Zuk, 13, of Riverdale Park said he heard that some states were trying to restrict African Americans from voting, similar to what happened in the 1960s. “They are asking people to present an ID when you’re voting,” he said.

Asked whether young black men are targets of racial injustice, Wesley cited the example of Trayvon Martin, who was killed in a February 2012 altercation in Florida that many believed was fueled by racist stereotypes. The man who shot him, George Zimmerman, was acquitted after a trial last year.

“We have an example in Trayvon Martin,” Wesley said. “All he was doing was walking down the street. That was another young man who could have done something great with his life, but it was ended because of somebody’s ignorance.”

The students applauded his remarks, and Braddock said she couldn’t have given a better answer.