When Larry Aaronson was growing up in Washington, D.C., racism was a wrought iron fence that separated white children in the sandbox behind his apartment house from the sandbox next door, where Black children played.
That memory loomed as a powerful image of the message segregated society sent about separating children by the color of their skin in the early 1940s, though it took years for him to fully grasp the implications. As a youth, he said in an oral history interview, “I was clueless” about race.
Then in the mid-1960s he became a teacher by accident, landing a job he hadn’t expected to get. Mr. Aaronson found his life’s calling and learned from his students and civil rights activists about how white history dominated textbooks, and how people of color were erased from school curriculum.
He said those first years of becoming “radicalized gradually by the experience of being a teacher” helped him understand that “public schools were the citadel of our democracy. Social studies, in particular, was the crucible.”
Mr. Aaronson, who later moved north and became a charismatic and influential teacher at Cambridge Rindge and Latin School, was 85 when he died Saturday in Neville Center at Fresh Pond in Cambridge. He had long been diagnosed with chronic lymphoblastic leukemia and had been living in Somerville.
With “A People’s History of the United States” as his textbook, Mr. Aaronson encouraged hundreds of students over the years to ask their own questions about the world around them.
“He told us to put away our other history books, the traditional ones, and he taught us Howard Zinn’s ‘People’s History.’ It was pretty wonderful,” said Rima Freeman, who was a Cambridge Rindge and Latin student when she first walked into Mr. Aaronson’s history class.
“As a teacher,” she added, “he made it fun to be in his class, to be part of alternative education and really learning.”
Mr. Aaronson, who retired in 2007, told students to keep learning and questioning after their school days were done and they went into the world — and to take action and never give up hope.
“I would describe him as the most intense optimist I’ve ever met,” said Nate Albert, a former guitarist for the band The Mighty Mighty Bosstones and a former student of Mr. Aaronson’s. “He just had this belief in us, and belief in the world: that you can make it right.”
The number of lives Mr. Aaronson touched seemed impossible for friends and admirers to calculate. More than 700 comments and condolences have been posted on Saturday’s announcement on his Facebook page that he had died.
“Larry, you are just simply one of the best to ever DO this THING called LIFE,” read one. “Your legacy will live on through so many of us.”
Along with teaching, Mr. Aaronson was a devoted photographer, recording so many school and community events and images from everyday life that an archivist has been tapped to sort through his voluminous collection.
His former students ranged from the famous, including Casey Affleck and Matt Damon, to seemingly every second or third person he passed on the street.
Walking through Cambridge alongside Mr. Aaronson was a stop-and-start affair.
“Literally, bus drivers would be waving from buses and shopkeepers would be walking out to say hi. And he taught them all,” said his cousin Sarabinh Levy-Brightman of Belmont, whose teaching years at Cambridge Rindge and Latin overlapped with Mr. Aaronson’s. “This was his community.”
Earlier this week, Cambridge City Councilors Marc McGovern and E. Denise Simmons and Mayor Sumbul Siddiqui sponsored a resolution honoring Mr. Aaronson’s life and work.
“Through his commitment to progressive education, his belief in the transformative power of public schools, and his unwavering encouragement of independent thought, Larry helped shape the lives and careers of countless young people, many of whom went on to dedicate themselves to public service and social justice,” the resolution said in part.
In the 2018 oral history conducted by Anne Gallivan and Norma Lesser, Mr. Aaronson recounted a conversation he had with a student in the 1960s, in Washington.
The skeptical student wondered if Mr. Aaronson would be like some white teachers who spent classroom time with students of color, only to leave and publish articles and books that catapulted them to more comfortable, higher-paying jobs far from the urban schools that provided their writing material.
Mr. Aaronson told the student he wouldn’t follow that path.
“I am not there to write the book,” he recalled resolving. “I am there to do the work.”
Lawrence Samuel Aaronson was born in Washington on Aug. 31, 1940, the only child of Eva Goldiner Aaronson, a social worker, and Abraham Palma Aaronson, who went by Paul and was an economist for the US Commerce Department, surveying the apparel industry.
Though he had no siblings, Mr. Aaronson was one of several first cousins in families that gathered weekly for Friday dinner at the cousins’ grandparents’ house.
He went to Sidwell Friends School and received a bachelor’s degree from Earlham College in Indiana.
Mr. Aaronson then graduated with master’s degrees from the Johns Hopkins School of Advanced International Studies and Columbia Journalism School before returning to Washington. He expected to be drafted during the Vietnam War and maybe become a journalist.
His mother pushed him to apply for a teaching job she had heard about. To his surprise he was hired without teaching credentials. To his relief he learned the job included a draft deferment.
Mr. Aaronson moved to Cambridge to enter an education doctorate program at Harvard University, which he left to work at the alternative Group School in Cambridge. He started working at Cambridge Rindge and Latin in 1977.
Upon retiring, he raised money to launch Social Justice Works! The Aaronson Fund, a nonprofit that supports Cambridge public school graduates working for social justice.
“My first year of teaching in D.C. transformed me into a militant teacher activist,” he said in 2008, at the nonprofit’s inaugural awards dinner.
By photographing local and school events even after retiring, Mr. Aaronson kept in touch with Cambridge. He even spoke a few times with future Boston Marathon bomber Dzhokhar Tsarnaev, who lived nearby and had “a heart of gold,” he told The Boston Globe.
When authorities released photos after the bombings, “I said, ‘that looks like Dzhokhar,’ and people have said to me, ‘why didn’t you call people and say you could identify this person?’ Because there is no way this could be this kid! There is no way in the world,” Mr. Aaronson told CBS News days later. “There’s nothing about him that would suggest anything like this — politics, religion, nothing.”
The devastating combination of knowing bombing victims and one of the bombers led Mr. Aaronson to have a nervous breakdown, he told the Globe a month later.
For Mr. Aaronson, who never married, his de facto family was his extended community of former students.
“He grew family around him,” said Freeman, who helped care for him in his final months. “You knew you were part of his family, and he held that with great care.”
A gathering to celebrate Mr. Aaronson’s life and work will be announced.
Hundreds visited as his health declined. When he was hospitalized a while back, he mentioned on Facebook that the end might be near, and an overflowing line quickly materialized. In his final weeks, a dozen people at a time visited him at Neville.
“The outpouring of love has really been something remarkable,” Levy-Brightman said.
“He was like a rock star,” Freeman added.
Never a haughty one, though.
“At the end of his life, he showed how we are all connected,” Freeman said. And in those last weeks, she said, he kept repeating that he was “so blessed.”
Globe correspondent Audrey Tomlin contributed to this report.
Bryan Marquard can be reached at bryan.marquard@globe.com.