Alum Rock is a census-designated place (CDP) in Santa Clara County, California, United States and a community of San Jose. The CDP, which excludes all annexed areas, had a population of 13,479 at the 2000 census. Alum Rock was named after a rock formerly thought to be composed of alum in nearby Alum Rock Park.Formerly a separate town, much of the community is unincorporated surrounded by incorporated San Jose; neighborhoods between White Road and Capitol Avenue are part of a city/county agreement for annexation.James Lick High School (which is part of the East Side Union High School District), Joseph George Middle School, Pala Middle School, and other schools in the Alum Rock Union School District serve the neighborhood. Near the center of the community is a small neighborhood commercial strip along Alum Rock Avenue at White Road.