Clairbourn School was started in 1926 by Mr. and Mrs. Arthur K. Bourne, a prominent San Marino, California, couple.

In 1931, the school needed a larger building and leased 3.5 acres on Huntington Drive in San Gabriel.

The home, located at 1861 Lombardy Road, was built in 1923 and was designed by the famous architect Wallace Neff.

In 1927, due to expanding enrollment, the informal school moved to the home of Mr. and Mrs. William W. Butterfield located at 1273 San Pasqual in Pasadena, California.

As enrollment continued to grow, the school moved a second time, to 245 West California Street in Pasadena.

By 1931, the school outgrew its building in Pasadena, and an estate of 3.5 acres on Huntington Drive near San Gabriel Boulevard was leased from Mr. George L. Platt, a successful dairyman of Los Angeles.

An additional five acres to the east was acquired in 1958 with the purchase of the Thompson estate, which included a large stately manor house, a swimming pool, and an orange grove.

In 1969, the elementary classrooms were upgraded, and an innovative hexagonal multi-classroom unit called The Gardner Building, was erected.

A brief portion of the assembly is called "Chapel," and it includes a simple inspiring message based on Clairbourn's Code of Ethics.

Common elements of the Chapel portion may include inspirational ideas and quotes, occasional simple Bible stories, a hymn, and the Lord's Prayer.