Jill Biden has gone to great lengths to keep her status as a political spouse under the radar from her students, to whom she is known simply as “Dr B”.

During her eight years in the Obama administration as second lady (she preferred the title “captain of the vice squad”), Dr Biden continued to teach English composition at Northern Virginia Community College (Nova). She even requested that the Secret Service agents who accompanied her to work come in disguise as students.

And when the 69-year-old becomes America’s next first lady, she will be the first to continue her professional career while in the role. But this time, when she returns to her day job in January, she may struggle to keep a low profile.

Student Karolina Straznikiewicz, 27, was taught by Dr Biden before she went on leave at the beginning of the year to join her husband, President-elect Joe Biden, on the campaign trail. Straznikiewicz spent her first lesson trying to work out why her teacher seemed so familiar.

“My brain was telling me that it’s so impossible that a second lady of the United States would teach in a community college around here … I am pretty sure that a lot of the students in the classroom had no idea who she was until the end of the semester.”

By now, though, Straznikiewicz thinks Dr B’s cover must be blown. This year, Dr Biden has darted across the country on the campaign trail as a valuable and energetic advocate for her husband, giving television interviews and speaking at drive-in rallies.

In an emotive and well-received Democratic convention speech this summer – delivered from an empty classroom at Brandywine high school in their home town of Wilmington, Delaware – she talked about the anxiety and heartbreak of the pandemic.

But she also conveyed a compelling sense of fun. During the convention, her granddaughters Natalie and Naomi described her as “not your average grandmother” and a “prankster”, recalling how she woke them up at 5am on Christmas Eve to go to a spinning class at SoulCycle and had picked up dead snakes while jogging to play practical jokes on family members.

“Unfortunately, she’s going to have everyone know who she is because there’s no way they can miss it,” Straznikiewicz said. She noted Dr Biden is a “tough grader” – a sentiment echoed in reviews on the Rate My Professors website. But that made getting her first A from her even more memorable.

“She gave me my paper back and she said ‘it was excellent, as always’. That has always just stuck with me and it totally flipped my thinking about my education.”

She never mentioned her husband, but one morning, Straznikiewicz remembers Dr Biden telling them about a dramatic interaction with a bat that got into their house. “It was so normal and so everyday stuff … She was just our regular professor.”

They studied Trevor Noah’s memoir Born a Crime, had conversations about race and current affairs and were asked to write about their own beliefs and experiences. Dr Biden’s sister-in-law, Valerie Biden Owens, gave a talk for students on female confidence.

Straznikiewicz is looking forward to seeing a community college professor become first lady. “I think she’s really going to stand up for us.”

Jennifer Lawless, a politics professor at University of Virginia, said Dr Biden will “knock down a glass ceiling” for first ladies and, along with Kamala Harris’s husband, Doug Emhoff, who is leaving his job to become America’s first ever second gentleman, represents an evolution of US politics.

“This is the first time that we’re seeing somebody say, ‘You know what? My previous life is important too and I’m not going to define myself entirely based on my husband’s job’,” she said.

The incoming first lady, who has been teaching for 36 years and has four degrees, moved to Nova from Delaware Technical Community College in 2009 after Barack Obama won the presidential election with her husband as his running mate.

“Everyone assumed I’d stop teaching and become a full-time second lady,” wrote Dr Biden in her book Where The Light Enters. “But not only did I want to keep teaching, I was being recruited by the dean at Nova.”

She went against the advice of senior advisers to do so because she “just wanted to do the thing I love best”. She said she “relished the tension” between the worlds of politics and education.

Dr Jimmie McClellan, the dean of liberal arts at Nova and Dr Biden’s supervisor, said: “We don’t treat her differently than anyone else. She’s a member of the faculty, and she has a cubicle like the rest of us … when she’s there we don’t really talk about what her husband’s life is like, we talk about education and teaching and our students.”

When she was second lady, he remembers her leaving with a stack of papers to go to a state dinner and returning with all of them graded the following morning.

McClellan said she was amazed by the stories of her students, many of whom are immigrants and refugees, and that she would leave post-it notes on the bathroom mirror at the vice-presidential residence so that her husband “would be aware of what students go through”. She also started a women’s mentoring programme.

As well as her career, which she has said has “sustained my passions and independence for more than 30 years”, family is central to what drives Dr Biden.

The oldest of five sisters, she was born in Hammonton, New Jersey, where her father’s name is on a second world war monument, and grew up in the Philadelphia suburbs.

At 18, when she started at the University of Delaware, she has said she “suddenly saw the cracks in our society up close”. She also got married to her first husband, a relationship that ended in divorce five years later.

In 1975, she went on her first date with the president-elect – then a senator, who had lost his wife and daughter in a car accident in 1972 – after being set up by his brother Frank, who she knew from university.

She wasn’t initially impressed by his “strait-laced” suit and loafers, but they ended up going out three nights in a row.

After five proposals, they got married in 1977 and Dr Biden became a stepmother to his two young sons, Beau and Hunter. Four years later she gave birth to a daughter, Ashley.

As an introvert, she has said she was “never a natural as a political spouse” but found her public voice speaking out on issues such as the military – especially after Beau joined the national guard – and cancer.

She has said her husband “tends to pull me out of my shell, and I help keep him grounded”. In 2003, she memorably wrote “no” on her stomach while wearing a bikini when party advisers tried to persuade her husband to run for president.

In the White House, her shared interest in the military with the former first lady Michelle Obama led to the creation of the Joining Forces initiative, which Dr Biden has said she will relaunch as first lady.

Obama has described Dr Biden as her “partner in crime” and “one of the most grounded people you’ll ever meet”. She also noted Dr Biden’s enthusiasm for practical jokes, which once led her to hide in the overhead locker of Air Force Two.

When Beau was diagnosed with brain cancer, the Obamas were the only people the Bidens told. His death in 2015 left Dr Biden “broken”, she said recently.

Jeremy Bernard, the White House social secretary and special assistant to the president for four and a half years under the Obama administration, said between the two couples there “was always a very warm and genuine fondness for each other”.

He said Dr Biden was welcoming from day one of him starting the job, and recalls spotting her the night before shopping in Whole Foods. When he mentioned it the following day he said she invited him to join her and her team for hot yoga.

Whenever she walked into a room she would acknowledge everyone there, a quality which he said is “very rare, not just in politics, but in general”.

He said she had a close relationship with her staff, who were part of her social life, and would write handwritten thank you notes after state and holiday dinners.

Dr Biden’s spokesman, Michael LaRosa, said she was currently spending time with her children and six grandchildren in Wilmington and was “focused on building her team and developing her priorities focused on education, military families and veterans and cancer.” Over the summer she was certified to teach virtually.

In his victory speech, President-elect Biden said: “For American educators, this is a great day for you all. You’re going to have one of your own in the White House.”

Katherine Jellison, a history professor at Ohio University, agrees. “To have the first lady as a cheerleader for American education, and in particular American public education, that will be a great thing for the education profession.”