Kamala Harris and Joe Biden were once again at loggerheads Wednesday night over busing for school desegregation and the vice president’s track record on the issue.

In the previous debate, Harris criticized Biden’s 1970s opposition as senator to court-ordered busing for school integration — a move that catalyzed Harris’s rise in the polls as well as a national discussion on the school segregation that persists in many American schools.

This time, the issue was raised by the debate moderators, who asked Harris whether Biden’s contention that the two candidates share a position on “busing” was true. Harris said their views differed sharply, and she would have opposed his efforts decades ago to limit the use of busing to desegregate schools.

“Had I been in the United States Senate at that time, I would’ve been completely on the other side of the aisle, and let’s be clear about this: had those segregationists their way, I would not be a member of the United States Senate,” she said. “So on that issue, we could not be more apart.”

But the California senator did not detail her views on how schools should be integrated Wednesday, a question that has dogged her since her criticism of Biden. “Senator Harris supports federal measures to increase school diversity, including resources for busing,” her campaign told Chalkbeat earlier this month, but didn’t spell out details.

Harris’ signature education policy proposal is a hefty raise for American teachers; she hasn’t released a proposal on school integration, though she did recently sign on to a federal bill to offer modest incentives for school districts looking to spur integration. Bernie Sanders, who appeared in Tuesday night’s debate, has released the most detailed plan on the issue of school segregation. A number of other candidates have said they support expanded integration efforts.

Biden responded to Harris that as California attorney general she did little to push for school integration in Los Angeles and San Francisco. “I didn’t see a single solitary time she brought a case against them to desegregate them,” he said.

Michael Bennet, the Colorado senator and a former Denver schools superintendent, chimed in to point out that schools remain deeply segregated by race and economic status.

“Our schools are as segregated today as they were 50 years ago,” said Bennet. “We’ve got a group of K-12 schools that are good because families can spend a million bucks and you’ve got Detroit Public Schools that are as segregated as they were.”

Schools do remain divided by race in many parts of the country, and the share of black students attending school alongside white students has declined in recent years. (Trends differ depending on how segregation is measured.) Research has also found that low-income students and students of color benefit from attending integrated schools.

Camille Respess contributed reporting.