Groton has a 480-acre campus, including academic buildings, dormitories, athletic fields, and undeveloped land for conservation. The campus was designed by Frederick Law Olmsted, designer of Central Park in New York City and the campuses of many high schools and universities. In 2018, Architectural Digest named Groton the most beautiful private high school campus in Massachusetts.

The School's core buildings are arranged around a (mostly) circular lawn, and "The Circle" is the primary metonym for Groton's campus. Walking across the Circle is traditionally forbidden, except while playing sports. Buildings on the Circle include St. John's Chapel, the Schoolhouse, the Brooks House and Hundred House dormitories, the Dining Hall, and the Dillon Art Center. Other facilities just outside the Circle include the Campbell Performing Arts Center, the Athletic Center, the Pratt and O'Brien Rinks (which convert to indoor tennis courts outside the hockey season), the Bingham Boathouse on the Nashua River, the Goodenough Solar Battery Farm, outdoor tennis clay courts and hard courts, and faculty homes.

St. John's Chapel was the second chapel built on Groton's campus. Although Endicott Peabody's Broad Church Episcopalian churchmanship contrasted with the Anglo-Catholicism of St. Paul's School, Groton donated its first chapel to the local Catholic community; this chapel was renamed the Sacred Heart Roman Catholic Church of Groton in 1904.Groton School is a private college-preparatory day and boarding school located in Groton, Massachusetts. It is affiliated with the Episcopalian tradition.

Groton enrolls about 380 boys and girls from the eighth through twelfth grades, dubbed Forms II-VI in the British fashion. Its $475 million endowment enables the school to admit students on a need-blind basis.Typically, 40-44% of students are on financial aid. Tuition, room, and board for the 2023-24 school year is $59,995, of which financial aid covers, on average, $46,519.

The school's list of notable alumni includes U.S. President Franklin D. Roosevelt. Although it no longer publishes its admissions rate, Groton was the most selective boarding school in the United States in 2016.

Groton School was founded in 1884 by Endicott Peabody, a member of a prominent Massachusetts family and an Episcopal clergyman. The land for the school was donated by two brothers, James and Prescott Lawrence, whose family home was located on Farmers Row in Groton, Massachusetts, not far up the road from Groton School's present location. Peabody was backed by Harvard president Charles Eliot and affluent figures of the time, such as Peabody's father Samuel Peabody, Phillips Brooks, William Lawrence, William Crowninshield Endicott, and J.P. Morgan. Groton School received early support from the Roosevelt family, including future President Theodore Roosevelt, and the dorms filled quickly.