The woman had her left arm and ankle tattooed sometime between the end of Dec 2012 and the end of last March, according to the board. An anonymous tip was provided to her school around last September, prompting an investigation by the board.
She has admitted to having the tattoos and says that she will have them removed surgically, according to the board.
The city's revised ethics code bans city workers from getting new tattoos. The ban, aimed at bringing discipline to city workers after a spate of scandals, is part of efforts led by the city's mayor, Toru Hashimoto.