Pete Sarna was under investigation for a drunken outburst following a charity golf tournament in mid-July. Sarna is accused of making racist remarks to an African-American sergeant.
A white officer who witnessed the tirade reported the incident to school officials.
In a letter to the Oakland school board, Sarna apologized for his actions. He said he would be entering an alcohol treatment program and will focus on his recovery and sobriety. Sarna's resignation ends the district's investigation.