In 1955, reflecting growth to the south, St. Peter Parish was carved from All Hallows Parish - which once extended 20 miles east to Sloughouse and 7 miles south to Florin. St. Peter School opened soon after, staffed by the Sisters of the Immaculate Heart of Mary.  Sister Mary Carmelita, IHM, served as principal and superior.

The "IHMs" last year at the school was 1970.  The Order was profoundly affected by Vatican II, and their departure from St. Peter was part of a far larger conflict between then Cardinal James McIntyre, Archbishop of Los Angeles, and Sister Anita Caspary (Humiliata), then the IHM Major Superior.  The California Sisters of the Immaculate Heart of Mary no longer exist as a canonical congregation.  The Immaculate Heart Community is its non-traditional successor, carrying on various works in education, such as Immaculate Heart High School, Los Angeles, and social justice.

The "IHMs" were succeeded by the Sisters Servants of the Blessed Sacrament, who now staff the Parish School of John Paul II.

The much-beloved Mrs. Roy Owens taught at St. Peter, but moved to All Hallows in 1967, for a total of over 30 years of service to south Sacramento Catholic schools. Mr. Joseph Lynn, following a remarkable tenure as Superintendent of the Sacramento City Unified School District, taught at St. Peter for 12 years.

All Hallows' former church and parish hall was physically moved to the Saint Peter site, becoming St. Peter's Parish Church. St. Peter Church seats 270.

Beloved Saint Peter Pastors include Monsignor James Church, Rev. Anthony Gurnell, and Rev. Sydney Hall.