The board issued the suspension Tuesday to Patrick Geller, 42, a science teacher at Cypress Bay High School in Weston, after students snapped photos of him taking a short nap during a class period, the South Florida Sun Sentinel reported Wednesday.
Geller told the school board he had been exhausted due to being up most of the night with a sleepless infant.
The board ruled he failed to supervise his students and disrupted learning in the classroom, and suspended him for misconduct in office and incompetence.
"People make mistakes but it's a safety issue," said Gracie Diaz, the district's chief human resource officer. "There's more intense pressure on educators."
Geller, who has been with the district since 2002, has the option of appealing the suspension before an administrative judge.