The term grading on a curve describes the various methods a teacher uses to adjust the scores that students get on an examination one way or another. Gradually, grading on a curve improves students’ grades by raising their actual scores by a few notches, probably improving a letter grade.  Several teachers use curves to adjust the tests’ scores, while others choose to adjust the letter grades assigned to existing scores.

The term “curve” relates to” bell curve,” a statistical tool that shows the expected variation or normal distribution of any data set.  It is referred to as the bell curve because once the data has been graphically plotted, the shape formed is a hill or a bell.  In a standard distribution, the data is mostly near the center; otherwise, the mean, having hardly any figures on the bell’s outer part, referred to as outliers.  Everything else being equal, whenever test scores are typically distributed, 2.1% of students who took the test are going to receive a letter score of A, 13.6% will receive a B, 68% will get a C, 13.6% obtains Ds, and 2.1% of students in the class receive an F.

Why Does a Teacher Make Use of a Curve?

A teacher uses a bell curve to analyze the test they have, assuming that a bell curve will be visible if the material for the test presented is an excellent one. For example, suppose a teacher takes a look at the scores of their class and finds that the average (mean) grade of the midterm exam they gave was more or less a C, and quite a few students obtained a B and D with a few students getting an A and F. In that case, they can say that her test was designed appropriately.

How Does a Teacher Grade on a Curve?

Grading on a curve can be done in several ways, and many are mathematically challenging. The following are the most popular methods that teachers use curve grades, presented along with the fundamental explanation for each method:

Add Points: Each of the student’s grades is increased by the teacher using points of a similar number.

• When Should it Be Applied? When the test is over, a teacher finds out that many kids could not answer questions 5 and 9 correctly. They may decide that the problems were written poorly or the instruction was inadequate. Thus, they increase the affected students’ scores by giving them credit for questions 5 and 9.
• Benefits: All of the students receive a better grade.
• Drawbacks: The students cannot answer questions 5 and 9 unless the lesson is retaught.

One hundred percent grade bump: A teacher raises the student’s score who received the highest score to a hundred percent and raises the rest of the student’s scores by the same margin.

• When Should it be Applied? If no student receives a score of 100%, and the nearest one happens to be 88%, they can add 12 percentage points to that student’s score so that it becomes 100%. They can also add that same percentage point to everybody else’s grade.
• Benefits: All of the students receive a higher score.
• Drawbacks: Students who receive low grades don’t benefit that much.

Who Threw Off the Curve?

Students in a class often accuse one person of throwing off the curve. So, what does that mean, and how were they able to do it? There is a theory that the student who aces an exam that everyone else has trouble with is going to “throw off the curve.” For example, if most testers earned 70% and only one student in the whole class got an A, a 98%, then when the teacher goes to adjust the grades, that outlier will make it more difficult for other students to get a higher score. Here are a few examples that use the two methods of curved grading from above:

• If a teacher wanted to increase the points for questions missed to everybody’s grade, but 98% is the top grade, she cannot add two more points as it will give that student a score of more than 100%.
• If the teacher wanted to bump students’ grades to 100%, they would only receive two additional points, which is not a remarkable jump.

Grading on a Curve – What Is Wrong with It?

When teachers use the curve as the basis for the grades, it puts a cap on the number of students who can excel.  Therefore, the forced grade becomes a disincentive for studying. Remember, the score is not the exam’s point; it is teaching your students about learning new things.