A Florida teacher says she was fired for giving a grade of zero to students who failed to turn in assignments.

Her parting message to her students -- written on a white board in the classroom and shared on her Facebook page -- has gone viral, drawing attention to the district's grading policies.

"Bye kids. Mrs. Tirado loves you and wishes you the best in life! I have been fired for refusing to give you a 50% for not handing anything in. (HEART) Mrs. Tirado."

Tirado was an eighth-grade social studies teacher in Port St. Lucie, Fla.

When students didn't turn in an assignment and she gave them a zero, she learned of a district policy that the lowest possible grade for any assignment is a 50.

She stood her ground, arguing that giving students half-credit for doing no work would not serve them well in the long run.

She wrote a follow-up message on her Facebook page Tuesday morning:

"Good morning! I am reading all the posts you have written and reflecting upon them. The reason I took on this fight was because it was ridiculous. Teaching should not be this hard. Teachers teach content, children do the assignments to the best of their ability and teachers grade that work based on a grading scale that has been around a very long time. Teachers also provide numerous attempts to get the work collected so they can give a child a grade. By nature, most teachers are loving souls who want to see students succeed. We do above and beyond actual teaching to give them the support they need. Are we perfect? NO. We make mistakes like all other human beings, but I know teachers work their butts off to help children to be the best people they can be!!!"