How Does Grading on a Curve Work?

September 1, 2023

how does grading on a curve work

As classrooms become more diverse and learning outcomes vary, educators seek innovative ways to fairly evaluate student performance. In the ever-evolving landscape of education, grading on a curve is consistently discussed. But what is grading on a curve? How does grading on a curve work? And how does grading on a curve compare to traditional grading? In this blog, we’ll explore the purpose, implementation, benefits, and issues that surround grading on a curve. Whether you’re a student curious about your academic fate or an educator exploring novel assessment techniques, soon you’ll understand the nuances of grading on a curve and how it compares to traditional grading methods.

First, why do educators use varying academic assessment methods?

Academic assessment as a practice, while useful in gauging student progress, is not without its pitfalls. Assessments can become overly standardized, favoring rote memorization over meaningful comprehension. This can stifle critical thinking and creativity, fostering a cycle of testing and forgetting rather than fostering holistic learning. Moreover, assessments may inadvertently exclude diverse learning styles. This means that students who struggle with traditional testing formats don’t have the opportunity to showcase the full spectrum of their abilities. High-stakes testing can also lead to anxiety and stress, hindering students’ overall well-being and learning capacity.

This preoccupation with grades can overshadow the intrinsic joy of discovery and prevent students from dynamically engaging with subjects. While educators continue to search for the best assessment methods, many view grading on a curve as one better alternative to traditional grading.

What is traditional grading?

In the traditional grading system, students are usually graded based on their individual performance in a course. This is reflected through various assessments such as tests, quizzes, assignments, and participation. These individual scores are often converted into percentages or points that are then used to determine a final grade, typically expressed as a letter (A, B, C, D, F) or as a numerical value on a fixed scale (e.g., 0-100%).

Typically, this system relies on an “absolute” scale where the criteria for earning a certain grade are fixed and predefined. For example, scoring 90% or above might be required for an A, 80-89% for a B, and so on. Essentially, students are evaluated based on how well they’ve mastered the material, regardless of how their peers perform.

Finally, what is grading on a curve?

Meanwhile, grading on a curve aims to address the potential variations that traditional grading systems neglect. Unlike traditional grading, where a student’s grade is determined by their individual performance against a fixed set of criteria, grading on a curve considers the distribution of all students’ performances in determining individual grades. This approach acknowledges that not every test or assignment is of equal difficulty, and that student performance can fluctuate accordingly.

So, how does grading on a curve work?

Here’s a simplified example to illustrate: Let’s say you have a class of 10 students who take a particularly challenging exam. The highest score is 85 out of 100, and the lowest is 45, creating a distribution that isn’t evenly spread. Some students have performed exceptionally well, while others have struggled. If you use traditional grading, anyone with a score less than 60 might fail the course (assuming 60 is the passing grade). Contrarily, if you decide to grade on a curve, the highest score of 85 might be set as an A, and all other grades would be adjusted upward accordingly.

After some thought, you decide to implement grading on a curve to account for the diverse abilities and the test’s varying difficulty. Now the exact method of curving can vary. Some common methods include:

Normal Distribution (AKA Bell Curve)

In this method, you aim to distribute grades according to a bell curve.

  1. Calculate the Mean and Standard Deviation: First, you calculate the mean and standard deviation of all the scores.
  2. Assign Grades: You give students who score close to the mean a C or its numerical equivalent. Then you give those who score one standard deviation above the mean a B and those who score one standard deviation below a D. While you give students who do exceptionally well (often those scoring two standard deviations above the mean) an A, and those who do poorly (typically two standard deviations below the mean) an F.

Linear Scaling

In this straightforward method called linear scaling, you add the same number of points to each student’s score.

  1. Identify the Highest Score: First, you find the highest score in the class.
  2. Calculate the Points to Add: Then you decide how many points need to be added to the highest score to make it 100% (or an A).
  3. Adjust All Scores: And finally, you add the same number of points to all students’ scores.

Percentile Ranking

Alternatively, you might choose percentile ranking and rank students based on their performance, then assign grades accordingly.

  1. Rank Students: First, you rank the students from highest to lowest based on their scores.
  2. Assign Grades Based on Percentiles: Then you might give the top 5% an A, the next 20% a B, the next 50% a C, and so on. The specific percentages can vary.


Or you might choose clustering, and identify natural “breaks” or clusters in the distribution of scores, then assign grades accordingly.

  1. Identify Clusters: You look for gaps in the distribution of scores where it makes sense to set grade boundaries.
  2. Assign Grades:  You give students within each cluster the same grade. For example, scores between 80 and 85 might be a B. Meanwhile, scores between 86 and 90 might be an A-.

In summary, no matter which way you choose to curve, students who might have struggled but performed relatively better within the context of the class could earn higher grades, reflecting their comparative achievement. And students who faced difficulties in comparison to their classmates could end up with lower grades while still having their efforts recognized within the curve.

Now let’s compare grading on a curve with traditional grading methods.

Traditional Grading Methods: Pros and Cons


  1. Clarity and Simplicity: Traditional grading methods provide straightforward benchmarks for students to understand their performance. And these fixed standards offer clear goals to strive for and a consistent basis for evaluation.
  2. Objective Evaluation: Standard grading is often seen as an objective measure of students’ performance. This means it focuses solely on individual achievement, disregarding subjective class-wide variations.
  3. Comparison Across Courses and Institutions: Traditional grading allows for easier comparisons of students’ performance across different courses and institutions. A certain grade in one class can be more readily understood in terms of achievement compared to other classes.

How Does Grading on a Curve Work (Continued)


  1. Ignores Contextual Factors: Traditional grading may ignore contextual factors affecting performance, such as test difficulty or the diversity of students’ backgrounds. As a result, it can lead to unfair evaluations.
  2. Inflexibility: Fixed grading standards make it difficult for educators to provide balanced assessments while facing challenging class dynamics or unfamiliar content.
  3. Limited Motivation: Students might become disheartened after receiving lower grades despite significant efforts simply because the assessment was unusually challenging. Consequently, this can affect their motivation and engagement in the learning process.
  4. Failure to Distinguish Among High Performers: Traditional grading might not differentiate well between top-performing students, making it difficult to identify exceptional accomplishments.

Grading on a Curve: Pros and Cons


  1. Fairness in Varied Difficulty: As mentioned, some assessments might be more challenging than others. Grading on a curve prevents exceptionally difficult tests from unfairly penalizing all students.
  2. Accurate Reflection of Class Performance: Curve grading offers a more accurate portrayal of a class’s overall performance. Additionally, it accommodates classes with diverse academic abilities and backgrounds, showcasing how students have performed against their peers rather than against a fixed standard.
  3. Motivation and Encouragement: By competing against their peers, some students might be more driven to excel and push their limits. Also, the prospect of earning a higher grade, even when the absolute scores are low, might encourage greater effort and engagement. (However, this benefit is inconsistent across different types of tests and situations.)
  4. Flexibility and Adaptability: Grading on a curve adapts to fluctuations in class performance. This flexibility can ensure a more balanced evaluation process when educators face challenging class dynamics or unfamiliar content.

How Does Grading on a Curve Work (Continued)


  1. Lack of Absolute Assessment: Critics argue that grading on a curve doesn’t provide an absolute measure of student knowledge because students’ grades are primarily determined by their peers’ performance.
  2. Disincentive for Collaboration: Students might view their peers as competitors rather than collaborators. And competition often causes students stress, hinders their confidence, and disrupts friendships.
  3. Complex Implementation: Grading on a curve demands careful analysis and calculations to ensure fairness. You saw the math! It’s tricky. Educators need to determine curve shapes, set appropriate standard deviations, and adjust for variations between assessments. This complexity can lead to inconsistency across different classes or educators.

Ultimately, the choice between grading on a curve and standard grading methods depends on educational goals, the nature of the subject matter, and the student population. Both approaches have their merits and drawbacks. But if you’re worried about how your school’s grading system is affecting your academic standing, find out how to properly calculate your GPA. More math!

How Does Grading on a Curve Work? — Final Thoughts

So now we’ve gained insights into the questions that echo through lecture halls and study spaces alike: What is grading on a curve? How does grading on a curve work? And how does it compare to traditional grading? While this method moves away from tradition and curves toward fairness and flexibility, it remains imperfect, much like any existing form of academic evaluation. Nevertheless, this alternative signifies educators’ and institutions’ commitment to finding more effective ways to enhance student learning. The curve isn’t just a grading tool; it’s a symbol of ongoing efforts to create educational environments where all students have the opportunity to succeed.