Immaculate Conception Parochial School first opened its doors to children of the parish in 1922. A small group of the Sisters of Loretto, whose motherhouse was in Nerinx, Kentucky, was placed in charge of the new school.

Original enrollment for the school numbered 83 children. By the end of the school year, there were 123 students. In the years that followed, a steady increase in the number of students necessitated enlargement of both the school and the convent. In 1936, a high school department with ninth and tenth grade was added. Two additional classrooms, a large auditorium and principal’s office were added to the original school building in 1938. However, due to low enrollment and insufficient finances, the high school section was closed in 1939.

Student enrollment had grown to 350 students by 1947, and by 1950 the registration had passed the 500 mark. The fifties and sixties saw many changes take place. More building took place. As the Sisters left, they were gradually replaced with lay teachers. The school grew to a sixteen-room school with double grades from first through eighth.

During the 1970s many schools throughout the Archdiocese of Los Angeles, including Immaculate Conception experienced a decrease in enrollment. By 1980, Immaculate Conception School was an eight-room school with only one class per grade. With the addition of a Kindergarten class in 1986, and a Transitional Kindergarten program in 2013, Immaculate Conception has become a ten-room school.

In the mid 2000s declining enrollment and financial concerns impacted Immaculate Conception and Annunciation, the neighboring school in Arcadia. In August 2010, it was decided to create one school on two campuses. Immaculate Conception Annunciation School opened the 2010-2011 school year as a combined entity of the two pre-existing schools. Grades K-4 were assigned to the Immaculate Conception campus and Grades 5-8 to the Annunciation campus in Arcadia.

The challenge of the new model that combined two schools from two parishes impacted the pastors, school leaders, students, families, and the parish communities. At the conclusion of the 2011/2012 school year it was decided to close the Annunciation campus and relocate grades 5-8 back to the Immaculate Conception campus. Immaculate Conception STEM Academy continues to maintain a positive relationship with Annunciation Parish and considers itself to be the Catholic school for Annunciation parish.

The Western Catholic Education Association (WCEA) granted Immaculate Conception Catholic School a certificate of commendation. It was fully accredited by the Western Association of Schools and Colleges (WASC) in 1976. The school has been granted both certification and full accreditation by the Western Catholic Educational Association and the Western Association of Schools and Colleges. Our current accreditation was extended through June 2021. This certification means that our school has met and must maintain strict standards pertaining to curriculum, teacher preparation, finances, physical facilities and equipment. Immaculate Conception continues to thrive and in the 2019-2020 school year has become a STEM academy, actively preparing students for a future in science, technology, engineering and math.