Smith said his last day would be June 30 so he can move his family to Chicago to be closer to his father-in-law, who is in poor health.
"The decision to leave at this time is very difficult," he wrote in the letter to OUSD board of education president David Kakishiba. "However, my commitment to my family first means this is the right decision at this time."
The board will consider his resignation at an April 10 meeting.
The board issued a statement about Smith's resignation Friday morning.
"The Superintendent will be leaving a legacy that Oakland can be proud of," the statement read. "We have no doubt that Oakland is ready for the work ahead."
Smith has served at the head of Oakland public schools for the past four years after he was appointed in May 2009 and assumed the post that July.
He had previously served as a deputy superintendent at the San Francisco Unified School District.
He received a bachelor's degree from the University of California at Berkeley and earned master's and doctorate degrees at UC Berkeley's graduate school of education.