There is no college-wide grading scale. Some departments do have a uniform grading scale. Check with your department chair to see if this is the case for the courses you are teaching.
There is no plus/minus system at Meredith. Final grades in undergraduate courses are A, B, C, D, and F. For graduate courses, grades are A, B, C, and F.
For more detailed information on grading, see Grading System in the Undergraduate Catalog and Grading in the Graduate Catalog.