The first school district in Decoto was not the Decoto School District, but the Cosmopolitan School District, which was formed on July 2, 1868, by the County Board of Supervisors. The first trustees were George Emmerson, Ezra Decoto, and F. W. Meyers. Land for the school was donated by Jonas Clark. The 1878 Thompson and West Atlas shows the school house as residing at the corner of May Road and Mission Blvd.
The school cost $1,100.54 to build. The school outhouse cost $75 to build. Furniture cost $170.92. The school was ready in October 1868 and opened its doors on October 28 with 20 students. The first teacher was Thorton Jones, who was paid $60 per month.
The next year the new trustees were John Whipple, Henry Smith, and Thomas Falvey. Whipple declined the office, so George Emmerson took his position on the Board.
Like schools today, funding was always a problem for the District. In 1870, the District put forth a tax for the school as a local ballot measure, and it failed. Another try was made in 1873 and it also failed. The school was so lacking in funds that the clerk of the Board donated the firewood for the school.
At some point the district was reformed into the Decoto School District. The last mention of the Cosmopolitan School District in the local paper was 1884.
The school building was sold to the May family, who moved the building to the end of May road and turned it into a house. In 1927, the house was given a serious make over, adding stucco over the wooden exterior. The building still sits at the end of May Road, across from the East Bay Regional Park parking lot.