How Does Grading on a Curve Work?

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As students, when it comes to tests and exams, we know the drill. You learn the content in class and then you revise it for yourself, you take the test and then you get your marks and grade back when it’s done.

However, it can be difficult to know where these grades actually come from. Of course, when you get your test back it will have been marked and these marks will be within certain boundaries that determine what grade you end up getting. However, you might be wondering how these grade boundaries are decided. One of the ways is through what is known as ‘grading on a curve’.

In short, grading on a curve works by altering students grades to meet the “bell curve”. This bell curve is the normal distribution of grades, meaning that most students will score in the middle with few getting the highest/ lowest grades. This can be done through altering grade boundaries to reflect the bell curve or by adapting the scores students receive. This may be done through bumping up a student’s score to 100%, creating a separate score, using the square root of the raw marks, or adding points to the original score.

Continue reading to learn more about how grading on a curve works and what it actually means. This article will take you through key details, from what grading on a curve can mean for students to what the pros and cons of grading on a curve can be.

What does grading on a curve mean?

For me, as a student, and maybe you too, grading on a curve is a term that was often mentioned in passing, but never truly explained. Irritatingly, this often ends up making it more confusing than anything else, even though it can be quite an important term for students to understand.

For us to be able to understand how grading on a curve works, we need to first understand what it actually is.

Grading on a curve is simply where students’ grades are adjusted in order to fit the “bell curve”. In this case, this “bell curve” is the “normal distribution” of grades. Thus, grades may be altered to be slightly higher or lower so that the same proportion of students are getting these grades.

As you might expect, for students’ grades to fit the “bell curve”, as a whole they should somewhat resemble a bell curve if plotted. By this, I mean that the majority of students are to have their scores in the middle with fewer students getting the highest or the lowest scores.

To put this into perspective, let’s take a hypothetical class of 10 students, who are given grades of A, B or C with A being the highest. For this class to perfectly meet the bell curve about 2 students would get a grade A, 6 students would get a grade B and 2 students would get a grade C.

You can learn more about grading on a curve by checking out this article by Thought Co. This page from Top Hat can also give you more details.

How does grading on a curve work?

As grading on a curve is where grades are altered to reflect “normal distribution”, it works by either altering the grade boundaries or altering the score students receive, independently from their raw marks. Let’s break down how each of these are done.

First of all, let’s start with what a grade boundary actually is. Grade boundaries are a fairly self-explanatory term in that they are the “boundaries” between each grade.

What this means is that grade boundaries show you the minimum number of marks that you need to get in order to receive a certain grade.

There are different ways that grade boundaries can be created. These can be done as base grades, for example, if 70% is always an A. In this case, to grade on a curve, the score or marks students get is what would need to be altered.

However, grade boundaries can also be created after the students have sat the exams and had their papers marked. In this case, grade boundaries can be set in order to reflect this bell curve as they already know how many students have gotten each raw mark.

You can learn more about grade boundaries by checking out this Think Student article.

Sometimes to distribute grades, students are given a score based off their raw marks and often other factors as well. This may be used to grade on the curve if teachers add points to these scores, bump someone’s score to 100% or use the square root of the percentage grade to calculate the adjusted score.

You can learn more about this by checking out this article by Thought Co.

Is it better to be graded on a curve?

There is a lot of controversy surrounding the use of grading on a curve. Some feel that it is an essential process. Whereas others feel that it adds superficiality to the grading system.

Like many things, there are strong arguments for both sides so in these next sections, we’ll break down what these are so you can make up your own mind.

We’ll start with the advantages that come with grading on a curve. Have a look at the following list to see what some of the main bonuses of the use grading of grading on a curve for students are.

  • Grading on a curve can boost some students’ grades- This is because students who would have score higher within the base grade boundaries may be pushed into the next grade boundary if these are slightly lowered.

Have a look at the following list to see what some of the main advantages of grading on a curve are for institutions.

  • Grading on a curve allows there to not be as much grade inflation– This is because the proportion of students getting each grade is fixed so it can’t keep getting higher and higher.
  • Grading on a curve allows teachers, exam boards and other institutions to see how easy or hard the exam was- This can be important to keep standardisation across the board. This may be for different classes, different school years or different exam sets.
  • When used on a large scale, grading on a curve can allow the teacher, exam board or alternative institution to get an idea of students’ capabilities– This is because with a larger sample, the bell curve model can be more reflective.

From these examples of pros of grading on a curve, we can see that these are rather limited and that there are more advantages for the teacher or institution than there is for students themselves. In the following section, we’ll look at the disadvantages of grading on a curve so we can compare these.

What are the drawbacks of grading on a curve?

Having now looked at the bonuses of grading on a curve, we can compare them to the negatives. These can even be further split up into the disadvantages to students and the disadvantages to teachers, exam boards and other institutions.

You can check out the following links to see articles from Top Hat, Academia Stack Exchange, LinkedIn and Through Education to find out more about both the pros and cons of grading on a curve, that have been discussed in the previous section and will be in the following ones.

What are the drawbacks of grading on a curve to students?

Look at the following list to see what some of the drawbacks to grading on a curve for students.

  • Grading on a curve restricts the number of students that can get the top grades– This makes it harder for students to perform as well on their exams.
  • If used in individual classes, grading on a curve can lead to unnecessary competition– This may even lead to there being more pressure on students and them feeling more stressed when it comes to exams. It may even lead to more tension within the classroom.
  • Grading on a curve may mean that individual students’ grades are overlooked– When used in individual classes, this can be disadvantageous as it would mean that students may not be given the individual attention they need.
  • Grading on a curve means that students grades are dependent on each other- This means that if 1 student was to get abnormally high, students who perform less well but would normally get a certain grade due to slight altering of grading on the curve, wouldn’t be able to get this grade, even if their own performance was consistent.

What are the drawbacks of grading on a curve to teachers?

In the following list, you can see what some of the drawbacks to grading on a curve are for institutions.

  • Grading on a curve can be less useful for smaller classes– This is because it works using proportions of students. In a smaller class, this proportion of students may even end up just being 1 or 2 people. This may lead to there being very small cut off points between each grade boundary.
  • Grading on a curve makes it difficult to measure how students actually performed– This is because their grades won’t be directly in relation to their marks on the exam, including how many questions they were able to answer and how many they were able to answer correctly.
  • Grading on a curve may mean that the standard changes– This is because while the exam should be standardised to ensure that each paper is roughly the same as previous exams or ones for different classes, the grades won’t be. This means that one student getting the highest grade on the exam for this subject/ lecture won’t particularly have the same skill set or level of knowledge as someone else who gets the highest grade in an exam from the same subject/ lecture.

From this you can see that there are many more drawbacks to grading on a curve than there are positives. This is particularly for the students themselves.

Can grading on a curve worsen your grade?

One of the main concerns students and their guardians may have about grading on a curve is how it can affect the student’s grade. Having looked at how grading on a curve can lead to bumping up students’ grades, you might be wondering if it could even make it worse.

As grading on a curve alters students’ grades to fit this “curve”, yes, it is possible for students to end up with worse grades. In the same way as students getting higher grades, this would only be a slight change, so it is unlikely for students to end up getting a much worse grade if this is the case.

You can read more about it in this response from Quora. Please note that Quora is a platform where anyone can answer so at times these may not be fully reliable.

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