The newest US supreme court justice and the bench’s first Black woman, Ketanji Brown Jackson, made a clarion call in favor of keeping race as one of many factors in US higher education admissions, as America’s highest court heard oral arguments on the issue of affirmative action.

The court is hearing two back-to-back cases brought against the University of North Carolina (UNC) and Harvard University by a conservative activist group, Students for Fair Admissions, but has not ruled.

The group aims to block colleges from diversifying their student bodies by taking race into consideration alongside academic achievement and multiple other elements, essentially claiming that such a policy gives an unfair leg-up to African American and Hispanic students, who are underrepresented on campus, and discriminates against white and Asian American students.

A supporter of affirmative action, Cecilia Polanco, previously told the Guardian that: “A lot of the assumption is that someone less qualified than me took my place. That’s not what affirmative action does. It offers support to students who are just as qualified and may have different life experiences.”

With a 6-3 conservative super-majority now on the court, affirmative action is deemed to be in jeopardy.

Jackson has somewhat controversially recused herself from the case being heard second, against Harvard, because she attended it, though other current supreme court justices also attended Harvard but have not recused themselves.

But Jackson spoke out stridently on Monday in the first case, involving UNC at Chapel Hill, when arguments were heard at the supreme court in Washington, where protesters on both sides gathered outside.

Against Patrick Strawbridge, a lawyer for the plaintiff, Jackson said: “You haven’t demonstrated or shown one situation in which all they [the universities] look at is race. They’re looking at the full person.”

Strawbridge said affirmative action violates the US constitution’s equal protection guarantees and federal non-discrimination statutes.

Jackson said: “What I’m worried about is that the rule that you’re advocating, that in the context of a holistic review process, the university can take into account and value all of the other background and personal characteristics of other applicants, but they can’t value race … that seems to me to have the potential of causing more of an equal protection problem than it’s actually solving.”

The justice was nominated in February by Joe Biden upon Stephen Breyer’s retirement. She was confirmed by the US Senate in April and had already been making an impact in the court’s new term.

On Monday she explained her reasoning to Strawbridge by giving a hypothetical example of two aspiring students applying to UNC.

She said: “The first applicant says, ‘I’m from North Carolina, my family has been in this area for generations since before the civil war, and I would like you to know that I will be the fifth generation to graduate from University of North Carolina. I now have that opportunity to do that. And in my family background, it’s important to me that I get to attend this university – I want to honor my family’s legacy by going to this school.’

She continued: “The second applicant says ‘I’m from North Carolina. My family has been in this area for generations since before the civil war, but they were slaves and never had a chance to attend this venerable institution. As an African American, I now have that opportunity and given my family background it’s important to me to attend this university. I want to honor my family legacy by going to this school.’

“Now, as I understand your no-race-conscious admissions rule, these two applicants would have a dramatically different opportunity to tell their family stories and to have them count.”

Jackson added: “The first applicant would be able to have his family background considered and valued by the institution as part of its consideration of whether or not to admit him, while the second one wouldn’t be able to because his story is in many ways bound up with his race and with the race of his ancestors.

“So I want to know, based on how your rule would likely play out in scenarios like that, why excluding consideration of race in a situation in which the person is not saying that his race is something that has impacted him in a negative way – he just wants to have it honored, just like the other person has their personal background family story honored – why is telling him no not an equal protection violation?”

Strawbridge said the university could take into account factors such as whether a student would be the first generation in their family to attend and whether they may be economically disadvantaged, but he said that race should not be relevant these days.