Grading on a curve system derives its name after a statistical function called the bell curve or normal distribution that represents the distribution of random variables as a symmetrical bell-shaped graph. Grading on a curve refers to the modification of students’ grades based on the performance of the class as a whole. Instructors resort to curving grades usually when the class performs lower than expected or if there was an issue with the assignment prompt.

This method is applied when the highest given grade in the assessment is subtracted from the highest possible grade for the same assessment. For example, if the highest grade for the assessment was 100%, and the highest given percentage grade was 90%, the difference is 10%. The instructor, in this case, will add 10 percentage points to each student’s submission.

### Curving Grades – Using the Flat-Scale Curve

Curving Grades – Using the Flat-Scale Curve
The instructor who implements the flat-scale curve will simply add the same point value to individual students’ submission, without calculating the difference between the highest possible and the highest given grades. For example, each student can receive extra 2 points because one of the test questions was not clear enough, and the majority of the class got it wrong.