The lesson, given to 11 and 12-year-olds, featured Michelangelo's David sculpture as well as his Creation of Adam painting and Botticelli's Birth of Venus.

One parent complained the material was pornographic and two others said they wanted advance warning before the lesson was given to their children.

Hope Carrasquilla, the principal of Tallahassee Classical School, handed in her resignation after an ultimatum from the school board's chairman, local media reported.

"It saddens me that my time here had to end this way," she told the Tallahassee Democrat.

Michelangelo's sculpture of the biblical hero David is one of the most famous objects in Western art history.

The statue's nudity has been part of a centuries-old debate about art pushing boundaries and the rules of censorship.

In the 1500s, when the Roman Catholic Church deemed nudity as immodest and obscene, metal fig leaves covered the genitals of statues like David.

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A reproduction of David was made in 1847 for display at the V&A. When Queen Victoria first saw the reproduction of, she was apparently so shocked by his nudity that a proportionally accurate fig leaf was commissioned to cover the genitalia, according to the gallery's website.

The leaf was kept ready any royal visits, when it was hung on the statue using two strategically placed hooks.