Saint Bernard began as a regional Catholic high school under the jurisdiction of the Diocese of Norwich and was dedicated on Sept. 5, 1956, by the Most Rev. Bernard J. Flanagan, Bishop of Norwich.
Saint Bernard opened as an all-girls' school in New London before instituting a co-educational program in 1958. In 1967, the present Uncasville complex was opened as a separate all-boys' school along with Notre Dame, an all-girls' high school in Norwich. In 1972 the schools of Saint Bernard, New London, Notre Dame, Norwich, and Saint Bernard Boys' High School, Uncasville, merged into one co-educational program on the Uncasville campus.
In 1997, Saint Bernard Academy was founded for grades 6 through 8 and encompassed an upstairs wing of the high school. On Aug. 17, 2006, the Most Rev. Michael R. Cote, D.D., Bishop of Norwich, announced a new administrative structure to unite Saint Bernard High School and Saint Bernard Academy under the name of Saint Bernard School. In 2011, Saint Bernard was welcomed into the Xaverian Brothers Sponsored Schools (XBSS) network of schools, becoming co-sponsored by the Diocese of Norwich and the Xaverian Brothers.