Founded in 1890, it took its present name and began a co-educational system with the 1978 merger of The Choate School for boys and Rosemary Hall for girls.

[7] Mary, an alumna of Miss Porter's School, was the great-granddaughter of Caleb Atwater (1741–1832), a Connecticut merchant who supplied the American forces during the Revolutionary War.

[8] William Gardner Choate (1830–1921) was a federal judge with the Southern District of New York from 1878 to 1881, before resigning to enter private practice.

[13] In 1936, Time reported that Rosemary Hall girls "work[ed] so hard [in the classroom] that when they get to Smith or Vassar it is often with a sigh of relief.

[citation needed] There was no formal relationship at the time with Rosemary Hall, but there were coeducational audiences for plays and recitals and Mary Choate hosted dances at the Homestead.

[21] St. John believed that expanding enrollment would improve the school's financial resources and allow him to offer more amenities to his students.

[citation needed] In the decade following the First World War, Choate sent 412 of its 618 graduates to Yale, Princeton, and Harvard, according to a 1928 edition of the school newspaper.

To accommodate Rosemary Hall's 230 students, Choate spent an additional $3 million to build what was essentially "a new campus" in Wallingford.

[31] In 1931, John F. Kennedy entered Choate as a third form (9th grade) student, following his older brother Joe Jr., who was a star athlete at the school.

[citation needed] Jack Kennedy—sickly, underweight, and nicknamed Rat Face by his schoolfellows—spent his first two years at Choate in his brother's shadow, and compensated for it with rebellious behavior that attracted a coterie.

Among these was Kennedy's lifelong friend Kirk LeMoyne "Lem" Billings, who kept an apartment in the White House during JFK's presidency.

[citation needed] It has been suggested that the oft-remembered quote from Kennedy's inauguration may have originated from a common refrain from Choate headmaster, George St. John's chapel talks: "The youth who loves his alma mater will always ask not 'What can she do for me?'

[16][36] Starting in the 1990s, Choate adopted a policy of shrinking the student body, growing its financial resources, and being more selective in admissions.

[51] Choate's curriculum includes elective and interdisciplinary courses, from astronomy and architecture to printmaking and post-modernism to digital video and development economics.

Other specialized programs include American Studies, creative writing, economics, FBLA, mathematics, philosophy, psychology, religion, debate, and the Fed Challenge.

[57] The Kohler Environmental Center, designed by Robert A.M. Stern Architects, opened in 2012 and is located on a 268-acre site in the northeast quadrant of the campus.

[59] Choate's Fed Challenge team was the 2009 national champion and has won the New England District Championship in 12 of the past 13 years.[when?]

In the 2012 American Mathematics Competitions (AMC) 12-A, Choate's team finished first in the nation, with the highest combined score of all 2631 participating schools.

[61] During the 2023–24 school year, Choate reported that it enrolled 861 students, employed 120.4 full-time equivalent teaching staff, and had a student-teacher ratio of 7.0.

[70] In 1893, Rosemary Hall were host to a cricket match with Mrs. Hazen's School of Pelham Manor, N.Y., that has been described by some as "the first interscholastic girls sporting event in American history.

In the audience was stenographer, Dudley Fitts, a critic, translator, and longtime teacher of Greek and Latin at Choate.

After an exchange of letters, Stein authorized Fitts to oversee publication of her talk in The Choate Literary Magazine.

It "occupies a unique place in Stein's corpus as a social text that carries the marks of its particular occasion ... direct address to her audience (around sixty boys, as well as faculty and some former students).