Does Grading on a Curve Help You? What Professors Don’t Always Explain

Students regularly ask this simple question: “Does grading on a curve help you?” The answer is not as simple as the question. In most cases, it is intended to help students by mitigating the impact of difficult exams. Still, it can also limit results, create competition, and obscure what grades are actually intended to measure.

To understand whether grading on a curve helps you, it is necessary to know:

• What curve grading is;
• How it works in practice; and
• How to dispute bell curve grading.

If you want to see how different curves might affect your results, check out our grade curve calculator and the following article: “Can Grading on a Curve Hurt You? What Students Should Know”.

Curve grading is a term that describes various methods used by teachers to adjust their students’ exam scores in some way. In most cases, curve grading improves students’ scores by a slight increase in their actual scores, which can result in a higher letter grade. Some teachers use curves to adjust exam scores, while others prefer to change the letter grades assigned to actual scores. A more in-depth discussion of the rationale behind these choices can be found in “What Does It Mean to Grade on a Curve? The Philosophy of Relative Assessment”.

The term “curve” refers to the “bell curve”, which is used in statistics to illustrate the normal distribution (i.e., the expected variation) of any data set. It is called a bell curve because, once the data is plotted on a graph, the line created usually forms a bell or hill. In a normal distribution, most of the data is close to the mean, with very few values outside the bell curve, known as outliers. Thus, if the test results were normally distributed, 2% of the students tested would get an A, 14% a B, 68% a C, 14% a D, and 2% an F.

For a visual and conceptual breakdown of these distributions, see “How Does Grading on a Bell Curve Work?”

There are several methods for implementing curve grading. Here are some of the most common methods used by teachers to grade on a curve, along with simple explanations.

If you’re interested in formulas, you can explore our article: “How to Grade on a Curve: Formulas and Methods”.

Add points

The teacher increases each student’s grade by the same number of points. This method is used after the test has been completed. For example, a teacher notices that most students answered questions 3 and 7 incorrectly. They may conclude that the questions were confusing or poorly taught; in this case, they add the score for these questions to everyone’s score.

• Pros: Everyone gets a better grade.
• Cons: Students learn nothing from these questions unless the teacher offers a review.

Increase the grade to 100%

A teacher raises the best student’s grade to 100% and adds the same number of points used to bring that student to 100% to the grades of all other students. For instance, if no one in the class scores 100% and the closest score is 88%, a teacher might determine that the test as a whole was too challenging. In this case, they can add 12 percentage points to that student’s score to bring it to 100%, then add 12 percentage points to the scores of all other students.

• Pros: Everyone gets a better grade.
• Cons: Students with the lowest grades benefit the least (22% plus 12 points is still a failing grade).

Use the square root

A teacher takes the square root of the percentage obtained in the exam and uses it as the new grade. The teacher believes that everyone needs a little help, but the grades are very scattered; there are not as many Cs as one might expect in a normal distribution. So they take the square root of the percentage obtained by each student and use it as the new grade: √x = adjusted grade. So you get, for example: actual grade = 0.90 (90%), then adjusted grade = √0.90 = 0.95 (95%).

• Pros: Everyone gets a better grade.
• Cons: Grades are not adjusted equally for everyone. A person who scores 60% would get a new grade of 77%, an increase of 17 points. The student who scores 90% only gains 5 points.

Each method defines what a curve is in grading differently, which is why curve grading outcomes vary significantly between courses.

Grading on a curve is actually quite controversial in academia. The main advantage of the curve is that it fights against grade inflation. For example, if a teacher does not use a curve, 40% of their class could receive an A, which means that the A does not hold much value. An A grade should mean "excellent" if it is to have any meaning, and in theory, 40% of a given group of students are not “excellent”.

However, if a teacher bases their grades strictly on the curve, this limits the number of students who can excel. Thus, an imposed grade discourages students from studying and fosters a toxic environment. Who wants a classroom full of students pointing fingers and blaming the one or two stars? A curve grading only helps students when teachers use it only to raise grades and create a collaborative atmosphere, so that students help one another improve their grades. At the end of the day, the purpose of a test is not the grade, but to teach students how to acquire new knowledge.

If you have ever felt disadvantaged after being graded with a curve, you may have wondered how to dispute bell curve grading. To be honest, challenging the concept of curve grading itself is a difficult task, but there are some steps that you can take.

1. First, ask for clarification about how the curve was applied.
2. Second, focus on concrete issues, such as ambiguous questions or grading inconsistencies.
3. Third, use the syllabus, rubrics, and assignment instructions as reference points.

In short, grading on a curve has long been a topic of controversy and remains so. Some argue that curves preserve the value of high grades, while others warn that rigid distributions can discourage effort and create unnecessary competition. In the end, the answer to “Does grading on a curve help you?” depends on how thoughtfully the curve is used.

Understanding what a curve in grading is may not change grading policies, but it can give clarity on a subject that may have seemed opaque at first glance.