Verb
grade on a curve (third-person singular simple present grades on a curve, present participle grading on a curve, simple past and past participle graded on a curve)
To use a grading system based on the scale of performance of a group to normalize a right-skewed grade distribution (with more lower scores) into a bell curve, so that more can receive higher grades, regardless of their actual knowledge of the subject; to curve a grade.
He asked the teacher to grade (the test) on a curve.