Former first lady Jill Biden often repeated the phrase that teaching was not simply a job but a fundamental part of her identity.

Biden stands out as one of the most prominent educators to live in the White House, with an education career that lasted four decades across high schools, colleges, and even a psychiatric hospital.

Classroom experience has influenced the nation's top office more than many realize: Nineteen presidents and first ladies have taught in K-12 settings. Business Insider assembled a roster of each person, leaving out non-presidential spouses referred to as acting first ladies.

Of these, both partners in just two presidential pairs - the Fillmores and the Garfields - served as teachers.

Several other presidents worked as college professors, such as Woodrow Wilson, Jimmy Carter, George H.W. Bush, and Barack Obama. Wilson spent more than 20 years in academia and remains the sole president with a PhD. Their positions differed, however, as some held only part-time or honorary posts.

Review every president who taught in K-12 schools, then every first lady.

John Adams

At age 20, Adams instructed students in a single-room schoolhouse in Worcester, Massachusetts, from 1755 to 1758, per the Worcester Telegram. Fresh from Harvard, he simultaneously began reading law with James Putnam, a local attorney.

Adams recorded favorable views of classroom life in his diary, noting that presiding over this small realm brought him the highest pleasure.

Andrew Jackson

Jackson served only briefly as a schoolteacher. He entered the role for a limited period after funds inherited from his Irish grandfather were depleted, according to The Hermitage.

Millard Fillmore

Raised in poverty on a struggling farm in upstate New York, Fillmore educated himself and later became a schoolteacher. Like Adams, he studied law while employed in the classroom, per the Miller Center.

Franklin Pierce

Nathaniel Hawthorne's biography notes that Pierce taught at a rural school during one winter break from college. Attending Bowdoin College in Maine, he was still a teenager at the time.

Pierce turned to legal studies soon afterward and gained admission to the New Hampshire bar in 1827.

James A. Garfield

Garfield took several teaching positions, chiefly to support himself while enrolled at Geauga Seminary in Chester, Ohio.

Although he performed well academically, he largely disliked instructing younger children in district schools, the National Park Service reported. He succeeded more with older learners and later taught at the Western Reserve Eclectic Institute, now Hiram College, where he eventually served as president.

Chester A. Arthur

Chester A. Arthur filled various school roles over the years. Like Pierce, he taught during winter breaks while studying at Union College in Schenectady, New York.

In 1851 he became principal of a school in North Pownal, Vermont. The next year he served as principal and teacher at a school in Cohoes, New York, where his sisters also worked, according to the Library of Congress.

Following Pierce's example, he read law during this period and passed the bar exam in 1854, per the Miller Center.

Grover Cleveland

The only president to teach in specialized education, Cleveland worked at the New York Institute for the Blind, now called the New York Institute for Special Education. He first connected with the school through his brother, starting as a secretary before becoming a teacher, according to the Institute.

Fanny Crosby, the blind mission worker, described Cleveland as a positive influence during her time on the faculty.

William McKinley

Like several other presidents, William McKinley briefly taught in a one-room Ohio school. His tenure ended early when he volunteered for the Union Army in 1861, according to the National Museum of the United States Army.

Warren G. Harding

Harding may have held the shortest teaching post among any president or first lady. The 29th president taught for a single term at a rural school near Marion, Ohio, per the Miller Center.

In a presidential address, Harding called teaching the greatest occupation and described it as the hardest work he had ever known.

Lyndon B. Johnson

Johnson taught at Welhausen Ward Elementary School in Cotulla, Texas, while still a college sophomore. The school, near the US-Mexico border, served students living in poverty. The National Park Service notes that Johnson launched and grew extracurricular activities such as spelling bees and organized sports, paying for supplies from his own salary.

Johnson considered teaching as a full-time career but ultimately chose politics.

Abigail Fillmore

Abigail Fillmore began teaching at age 16. She later accepted a position at New Hope Academy in New Hope, New York, in 1819, according to the White House Historical Association.

She met Millard Fillmore when he was a 19-year-old student at the academy, and they married seven years later. Abigail Fillmore kept teaching after marriage, becoming the first first lady to maintain a profession following her wedding.

Lucretia Garfield

Like her husband, Lucretia Garfield taught in Ohio, specifically in Ravenna, Bryan, Chagrin Falls, and at the Brownell School in Cleveland, per the National Park Service.

Helen Taft

Taft wrote in her memoir that her decision to teach stemmed from a desire for an occupation more fulfilling than dancing and amateur theatricals.

In the 1880s she taught for two years at private schools in Walnut Hills, Ohio.

Grace Coolidge

Coolidge accepted a teaching role at the Clarke School for the Deaf in Northampton, Massachusetts. Her time there sparked a lifelong commitment to supporting disabled children, which she advanced as first lady through fundraising and public awareness efforts, according to the Coolidge Foundation.

After leaving the White House, Coolidge chaired the Clarke School's board of trustees and continued her advocacy until her death in 1957.

Lou Hoover

Hoover earned her teaching certificate from the San José Normal School, now San José State University, in 1893. Just one year later she left teaching to pursue geology instead.

During her short time in the classroom she likely taught at a local school in Monterey, California, per the Mayo Hayes O'Donnell Library.