El Monte School District held their classes in the Clarence Foster home until a school was constructed in 1915 on the south bank of the San Diego River. One acre of land was donated by the Bach Development Co. which had subdivided the El Monte Ranch in 1913.

School opened September 1915 with 15 pupils, the number needed to meet the state law. School opened with the minimum number of pupils allowed by law by the early entrance of Arthur Foster, who was not yet five years old. Some of the first students included Grace Wilkinson, Leda and Ruth Hartung (who came on their mules—Judy and Kit); Valois, Verna, Norma, Doris and Glen Melville; Art, Ruth, Dorothy, and Hazel Foster; Augusta Vanoni; and Florence Lucille, Irene and Frank Bogue. The first teacher was Laura L. Ehlers. The first trustees were Clarence Foster, John W. Fetters and Mary Fetters.

The school had been in operation less than four months when on January 13, 1916 the San Diego river changed its course and rampaged down the valley taking several homes and the new school house. It was washed away — and it was back to the Clarence Foster living room.

Item from the San Diego Newspaper, January 27, 1916:

"The El Monte School House above Lakeside has vanished like a ghost in the night! Neither on the banks where the recent floods waters have receded, nor in the river district, brought this word today to the County Superintendent of Schools. Superintendent West furnished a clue when he said he thought he had recognized the roof of the School House in the river bed near Lakeside. Fetters (Trustee) is of the opinion that the school house has disappeared by sinking into the loose, water-soaked earth. He says an attempt will be made to dig or locate it, so that it can be dug up. Meanwhile school is being held in the Clarence Foster home.

School classes were again held in the Clarence Foster living room. Dorothy Foster Lyons was a pupil in the school and she recalls the first day she started to school even though she only had to walk around the porch to the front door — she was late. Dorothy later earned her teaching credentials and taught in the Lakeside District for 24 years, mostly in Kindergarten, until she retired 1974.

A new school was built in 1917 by John W. Fetters on higher ground (five acres) donated by John Wilkinson. The El Monte school building was abandoned July 13, 1923 when the El Monte School District united with the Lakeside Grammar School District and the Lakeside Union School District was formed. The El Monte School building was sold to John Wilkinson in 1936 and the land was deeded back to him. The school house was then remodeled into a private residence.