Shelby County Schools found grade discrepancies at the school in the fall of 2016.
The district investigated four employees, including Quinn, head football Coach Teli White and two other male coaches.
“When I walked in the door, I felt like they were out to get me. There was nothing I could say,” said Quinn.
Quinn alleged in the lawsuit that she was treated differently than the others involved.
"Despite the fact that the investigation is 'ongoing,' Ms. Quinn is the only employee who was prematurely terminated from her position," the lawsuit said.
"All of the similarly situated young male employees have retained their employment with Shelby County Schools," the lawsuit contended.
“We did an extensive investigation, and (were) only able to document one person. That one person was Shirley Quinn," said Dorsey Hopson, the district’s superintendent.
Hopson said the investigation in the fall of 2016 only connected grade changes to Quinn's computer.
“Although we thought there had to be more, but in the spirit of due process, just because you think somebody did something, you have a strong, sneaky suspicion somebody did something, you can't act on them,” said Hopson.
Quinn was fired before Ronnie Mackin penned his explosive resignation letter, which launched new investigations into the district’s grading practices.
In the lawsuit, Quinn demanded to be reinstated and to be reimbursed for lost wages and benefits.
A Shelby County Schools spokesperson said Friday that the district is unaware of the lawsuit, which was filed three days ago at Shelby County Circuit Court.