It is located in the Roman Catholic Archdiocese of Los Angeles and sponsored by the Sisters of St. Joseph of Carondelet.

The high school was founded by the Sisters of St. Joseph of Carondelet (CSJ).

Saint Joseph is a National Blue Ribbon School and is accredited by the Western Association of Schools and colleges (WASC) and the Western Catholic Education Association (WCEA).

Admissions to Saint Joseph is based on entrance examination, activities, arts and athletics.

Admission decisions are based on interview of parents and (separately) the student; letters of recommendation from teachers; participation in activities, community service, arts and/or athletics; grades from elementary school, and entrance test scores.