Many, or perhaps most, law schools in the United States grade on a norm-referenced grading curve. The process generally works within each class, where the instructor grades each exam, and then ranks the exams against each other, adding to and subtracting from the initial grades so that the overall grade distribution matches the school's specified curve (usually a bell curve). "The curve" is the permitted range of each letter grade that can be awarded, for example, 0-3% A+, 3-7% A, etc. Curves vary between different law schools, as do the rules for when the curve is mandatory versus suggestive. It is common for the curve to be mandatory for first-year ("1L") courses, and for classes above a certain size.