In absolute grading systems, like those common to many high schools in the United States, there are set levels that a student must achieve to receive a certain grade. Generally, a maximum possible number of points is calculated, and levels are carved out of those that reflect different performance levels. In these systems, the student is competing against himself and the test rather than against other students for certain grades.
One example of an absolute system is the grading system for high schools in the United States. In much of the country, grades are offered on five levels, those being A, B, C, D and F. Normally an A, the highest grade, is awarded to those who earn 90 percent or more of the total possible number of points. A plus or minus may be affixed to the letter to denote what end of the 10 percent differential the student is on. For example, an A- may be given to those who receive between 90 and 92 percent of the points.
The other common type of grading system is relative grading. In this system, students compete against one another for an unchanging or minimally flexible number of slots for each grade. This style of grading is common in many college classrooms and prevents grades being lowered by an overly difficult test or being raised by an overly easy one. This is also known as "grading on a curve," because many instructors give low numbers of A's and F's and give more C's than anything, creating a bell-curve shape for grades when charted.
Many college students and professors are familiar with the notion of "grading on a curve." One type of curve grading that has become popular lately involves those receiving a point total in or above the 90th percentile receive an A, and those in the lowest 10 percent receive an F. 70 through 89 may receive a B and 11 through 30 may receive a D. The rest, 31 through 69, for example, would receive a C.