The school is within the Glenmont census designated place,[6] has a Silver Spring postal address, and is in close proximity to Layhill.

Barrie was described by Mrs. Seldin as a progressive country day school, directly influenced by the work of John Dewey, Maria Montessori, Alfred Adler, and Anna Freud.

[citation needed] It was an anomaly among private schools in Washington, D.C., for much of its history because of Mrs. Seldin's then-controversial beliefs about integration, creating a socioeconomically diverse population, and her decision to offer a year-round program and extended hours to serve working parents.

[citation needed] Although the name Montessori was rarely used in describing Barrie School during those years, the program was heavily influenced by Maria Montessori's philosophy and program, including practical life, integrated learning and project-based collaborative learning, multiple age class groups, and a culture of partnership between students, parents, and staff.

[citation needed] In the 1950s, Mrs. Seldin purchased a 45-acre (180,000 m2) country estate on Layhill Road in rural Montgomery County, Maryland.

In 1976, the Fern Place campus was closed and the remaining Middle and Lower School classes were moved to the Layhill Road property, with room for 265 students.