In 1917, a small school was opened and named San Marino School. After growing and adding a Kindergarten in 1929, the name was changed to Henry E. Huntington School. The covered archway which joins the campuses of what are now Valentine School and Huntington Middle School was once a bridge across a culvert that ran through the property. Valentine School, named for San Marino's second mayor, William L. Valentine, opened in 1938 with 380 students in its Kindergarten through fourth grades. It was the second primary school to be built in the district, the first being Stoneman in 1930.
When Valentine School opened in 1938 as an expansion of the Huntington School, Miss Edrys Nagle assumed the role of first principal. Miss Nagle continued as principal until 1963, and was then followed by Mrs. Annalee G. Bennett. Mrs. Bennett retired in 1969 and Miss Eleanor Pratt became Valentine's third principal. When Miss Pratt retired in 1978, Mr. Chet Gilgen served as interim principal for one year. In 1979, Dr. Carol Lambert became the fifth principal, followed in 1985 by Mrs. Mary Meye. During the summer of 1995, Mrs. Meye retired, and Mrs. Valerie J. Kates, formerly a Resource Specialist at Valentine, became the seventh principal. After her retirement in 2004, Dr. Tray Schreiber served as principal from 2004 until June, 2009. For the school year 2009-2010 Ms Billie Jean Knight served as an interim principal. Mrs.Colleen Shields became principal in 2010 and served until 2020. In 2020, Mrs. Alana Fauré became the eleventh principal in the history of Valentine School.
The original Valentine rooms are those on the street side of the long corridor, and all except one room of the four westerly fingers which extend out toward the playground. All were constructed as a Government Work Projects Administration Plan at a local taxpayer cost of less than $150,000. The lower Kindergarten room, the fourth grade rooms (fourth grade was added to Valentine in 1960), the Multi- purpose room, and one classroom (the science lab) nearest the Community Church have been added since.
In 1987, Valentine School was declared an Historical Landmark. In 1993 the original building went through a state-funded modernization project. Twelve of the classrooms, the teachers' lounge and workroom, the office, and the hallways were made handicapped- accessible. The twelve classrooms, office, and lounge were painted, carpeted, and air-conditioned, and new heaters were installed. During the summer of 1996, four relocateable classrooms were added to Valentine school, to enable a reduction in class size at the primary grade level. Shortly afterward, Valentine was designated a California Distinguished School validating the excellent instructional program provided at the school. From 1998 through 2003, the whole school underwent modernization. All classrooms were updated and a completely new building was added that included new science and art labs, several new classrooms and office facilities. All modernization was due to the overwhelming generosity of the community approved facility bond issues.