Marie Conley, the school crossing guard who was fatally struck in a Dorchester crosswalk while shielding a 10-year-old boy from an oncoming car three years ago, was named yesterday as the winner of one of the nation’s highest honors for civilians.

Conley is one of three recipients of the Citizen Service Before Self Honors bestowed by the Congressional Medal of Honor Foundation in Washington, D.C.

Conley and two Pennsylvania men — Timothy Brooks of Philadelphia, who saved a woman and her three children after their tour boat sank last year, and Dr. Pascal Spino of Greensburg, who has treated poor children, often for free, over a long career in medicine — will be honored Friday during a ceremony at Arlington National Cemetery. The awards, aimed at recognizing unsung heroes, are presented by the fewer than 90 living Medal of Honor recipients.

Conley was run over and fatally injured outside the Mather Elementary School in Dorchester in 2008, but managed to prevent a student from walking into the path of the car. The 87-year-old driver of the car, who said he didn’t see Conley even though she was wearing her florescent vest, was sentenced to probation, after Conley’s family asked a judge that he be spared jail, as long as he agreed to give up his driver’s license.

Michael Conley, one of Marie Conley’s four grown children, said the award was bittersweet because it was posthumous, but still very much appreciated.

“My mom was a selfless person, who thought of others before herself, so it’s nice that she’s being honored like this,’’ he said. “She was just a neighborhood person, a single mom who worked two jobs to raise four kids. She really cared about the kids at that school.’’

Two years ago, Marie Conley was posthumously given the state’s highest award for civilian bravery, the Madeline Amy Sweeney Award for Civilian Bravery, named for the American Airlines flight attendant who relayed critical information about the hijackers on Sept. 11, 2001.

Michael Conley said more than a dozen family members are planning to attend Friday’s ceremony, which will be held next to the Tomb of the Unknowns, where General James Amos, commandant of the Marine Corps, will give the keynote address.

Marie Conley’s son Chris is a Marine who has served several combat deployments in Iraq and Afghanistan.

Kevin Cullen can be reached at cullen@globe.com.

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