BERKELEY, Calif. — In 1967, the superintendent of the Berkeley, Calif., school district had resolved to desegregate the city schools. “We will set an example for all the cities of America,” he wrote in a report called “Integration: A Plan for Berkeley,” which he presented to the Berkeley Board of Education. “The children of Berkeley will grow in a community where justice is part of their pattern of life,” the report stated.

Several years later, a young girl named Kamala Harris, the daughter of an Indian mother and a Jamaican father, boarded a school bus — part of that school integration program that would change her, the city and the country’s conversation about racial politics.

“There was a little girl in California who was part of the second class to integrate her public schools, and she was bused to school every day, and that little girl was me,” Ms. Harris, now a senator and candidate for president, said on Thursday evening onstage at the Democratic debate. She was directly addressing former Vice President Joseph R. Biden Jr., and what she described as his history of opposition to mandatory busing.

In that moment, Ms. Harris invoked a complex part of American history, and the way cities tried to address how segregated the country’s classrooms remained more than a decade after Brown v. Board of Education was decided. She also made plain how the conversation about integration that took place in Washington and in cities around the nation directly affected the life of a first grader on a school bus. She and her peers played hand-clapping games to pass the time, one classmate remembered, aware that their bus ride took them to a neighborhood different from theirs, but not that it was something a superintendent had to fight for.

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Ms. Harris attended a Montessori school for kindergarten and joined Ms. Porter at Thousand Oaks in first grade. During the debate, she described herself as “part of the second class to integrate her public schools,” and her classmates were the second group of kindergartners to be bused to schools outside their neighborhoods. A campaign spokeswoman confirmed that Ms. Harris joined the class in 1970, her first grade year, which was the third year of integration. The school had been 2.5 percent black in 1963. In 1969, it was 40.2 percent black as a result of integration.

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Most Americans at the time were in favor of integration, but few thought busing was the best method, according to a 1973 Gallup poll. Given alternatives like low-income housing in middle-income areas or changed school boundaries, only 9 percent of blacks said they preferred busing, and just 5 percent of whites did.