1921 - 1945

In 1923, Ella Cannon Levis became co-headmistress with Mary Edwards Calhoun. As a result of increasing enrollment in this time of prosperity, the school moved to new, larger quarters at 309 W. 92nd Street. A fifty-by-forty foot gym was built on the roof to support a new emphasis on physical education in the curriculum (instead of doing calisthenics in the classroom, between the desks!). A Parent-Teacher Association was formed, asking for $3 in dues from each family, and around 1924, the school name was changed to The Calhoun School at the request of parents. In the 1920s and 1930s, community service projects were increasingly available to students and alumnae, who actively supported the University Settlement on the Lower East Side and helped organize the first Well-Baby Pre-School Clinic in New York City.

Music class, 1922.  The aim of The Jacobi School, as written in the 1920 Handbook, was "the well-rounded development of the students," with much attention given to activities "beyond purely scholastic training."

Private school enrollment fell during the hard times of the depression in the1930s. With a decreasing number of younger students applying to private schools, Calhoun finally closed the elementary school in 1937 and devoted its 92nd Street building to the increasing demands of a modern secondary school program for girls, grades 7–12. In 1939, Miss Calhoun incorporated the school as a non-profit institution to ensure its future success. No longer privately owned, Calhoun became a role model for what is still today a unique constituency Board of Trustees with representatives from parents, faculty, alumnae/i and friends. In the early ’70s, students were added as non-voting representatives.

During the late 1930s and the war years, members of the Calhoun community watched events in Europe and Asia with increasing concern. Students raised money to provide scholarships to refugees from Germany. Parents rolled bandages for and made donations to the Red Cross, and the school became a neighborhood collecting agency for paper, rubber, and bandages. Preparing Jewish girls to deal with anti-Semitism in colleges in the United States was also a concern. 

Back in 1944, Calhoun's Social Service Club gathered rags and tin for the war effort.

Social events continued in 1942–43 despite the war. At Christmas time, the school prom was held at the Plaza Hotel. The Calhoun glee club made its debut at the Song Festival at Carnegie Hall, sponsored by The Guild of Independent Schools for the benefit of the Greater New York Fund. In late spring Calhoun enjoyed its annual boat ride up the Hudson to Indian Point, for a day of baseball, swimming and boating. There was a father-daughter debate in the 1940s and a debate with boys from The Dalton School.

Retiring in 1942, Miss Calhoun became Chairman of the Board, pursued her interests in World Federation, supported the work of the Society of Friends, and left bequests to Martin Luther King, Jr. and the NAACP as well as to her sister and the educational institutions with which she had been associated. Miss Levis continued as Head until her retirement in 1946.