[1][2] St. Mark's was founded in 1865 by Southborough native Joseph Burnett, a chemist and entrepreneur who amassed a large fortune manufacturing surgical anesthetic, cough syrup, hair tonic, cologne, soda, sausages, bottled milk, and most famously America's first commercially viable vanilla extract.

The staunchly Episcopalian board of trustees clashed with Peck, a layman with (according to Pomfret) "progressive tendencies.

[5] The St. Mark's trustees responded to this crisis by appointing Groton School English teacher William Greenough Thayer as the new headmaster.

[22][23] Thayer's relationship with Lawrence gave St. Mark's access to the bishop's vast network of donors.

"[25] He continued Peck's project of recruiting the sons of American business titans, adding William Kissam Vanderbilt and Joseph Pulitzer to the parent list.

[13][26] A study of the St. Mark's class of 1906 found that 79% of the graduates' fathers were listed in the Social Register; 59% had attended Ivy League schools; and 54% worked in finance, law, or other professional services.

[31] Edward Hall recalled that "[e]xcept for a handful (it was seven in 1927) of competitive places, priority of application governed likelihood of acceptance.

Getting into St. Mark's in the 1920s was a little like getting into the Somerset Club of Boston: a boy's name was put down within hours or days of his birth if he was to have a chance of acceptance.

He increased the number of students admitted by competitive examination to ten and based the remaining admissions on a mixture of factors, which still included priority of application but also interviews and geographic diversity.

[36] After the war, he joined the predecessor of the National Association of Independent Schools; when NAIS was created, he became its first president.

[37] William Brewster (h. 1943–48) made the first concerted attempts to change the school's image as an institution of social elites.

[44][45] In the 1960s, the school took its first steps towards coeducation by agreeing to move the all-girls St. Margaret's School in Waterbury, Connecticut to Southborough; St. Mark's hoped that St. Margaret's would accommodate female students who wished to attend St. Mark's but could not due to the boys-only policy in force at the time.

[45] In the 21st century, St. Mark's has focused on expanding its facilities and raising money for teacher salaries and student financial aid.

[52] The production team shot footage in the dining hall, headmaster's office, and basketball court.

[53] Although the St. Mark's campus has been modernized since the 1970s (when the movie is set), anachronistic fixtures were temporarily removed to accommodate the production crew.

St. Mark's has educated several Olympic athletes, including Truxtun Hare in track and field (also one of only four four-time College Football All-Americans),[60] Suzanne King in cross-country skiing, Scott Young and Greg Brown in ice hockey,[61][62] and Chris Sahs in rowing.