The announcement was made shortly before 6:30 p.m. Monday during a meeting of the school board, which met to discuss the situation after Cook admitted to plagiarizing a commencement speech he gave.
Cook will stay on as a board member.
Cook admitted that he took parts of a 1998 speech from Donna Shalala, former secretary of Health and Human Services, and passed them off as his own words during a speech at Orange High School.
He later apologized. But the school board came under increasing fire in recent days as parents and students sought disciplinary sanction against Cook.
Cook said he made up his mind to resign minutes before arriving at Monday's meeting.
The school board did not allow public comment on the resignation. New chairwoman Brenda Stephans said board members expressed their disappointment with Cook behind closed doors.
Cook said he intends to run for re-election in July.
"I think the children and the school district still need a voice like mine," he said.
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