Was a Florida history teacher fired for being too tough? When some of Diane Tirado's eighth grade students didn't turn in an assignment, she gave them zeroes. However, she said the Port St. Lucie School District mandates that the lowest possible grade is 50 percent even if students turn in nothing, apparently for just showing up. Tirado said she refused to give out any percentage points if the students did nothing. She was fired on Sept. 14, she said.