Comparing this year’s top student with past performers makes no sense

Jun 28, 2025 Features / Columnists, Peeping Tom

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Kaieteur News – The announcement of the National Grade Six Assessment (NGSA) results always generates excitement and, sometimes, confusion. This year was no different. The country has been celebrating the stellar performance of a young girl who achieved a perfect score, meaning she earned the highest possible mark that the system could award. And yet, some have bizarrely begun comparing her total score with those of previous top performers—insisting that hers is “lower.” But in doing so, they reveal a fundamental misunderstanding of how NGSA scores are calculated.

A perfect score means that the student could not have done any better. It means that, based on the structure and scaling of the NGSA scoring system for this particular year, she reached the ceiling. There is no “better” than that.

To understand why these comparisons across years are misleading, one must understand how NGSA scores are actually derived. Thankfully, educator Sir Leon recently offered a useful public explanation on Facebook, helping to demystify the process. Here’s how it works.

When a student writes the NGSA, they sit examinations in four subjects: Mathematics, English, Science, and Social Studies. Each of these papers is marked, and the student receives what is called a “raw score”. This is simply the number of points the student earned, often out of 60. For example, if a student answer 54 out of 60 questions correctly in Mathematics, their raw score for that subject is 54.

However, raw scores alone are not enough. Why? Because not every test is the same level of difficulty each year. One year’s Math paper might be a bit tougher than another year’s. Or the Science paper might have questions that, on average, students find easier than before. So, comparing raw scores from different years—or even from different subjects in the same year—doesn’t always give a fair picture.

This is where “standardization” comes in.

To account for variations in difficulty and performance, raw scores are converted into standardized scores. This is done using the formula:

Standardized Score = (Raw Score – Mean) / Standard Deviation.

Let’s me explain what this means. The mean is the average score of all the students who wrote that subject. The standard deviation is a measure of how spread out the scores are. It tells you whether most students scored around the same mark, or whether there was a wide range of performances.

By subtracting the mean from the raw score, you find out how far above or below the average the student was. Dividing by the standard deviation then tells you how significant that difference is, in standardized terms. The result is a score that shows how well the student did relative to everyone else—not just in terms of raw marks, but in the context of how difficult the test was and how others performed.

This is important because it creates a level playing field. A raw score of 50 in a difficult Math exam might actually represent better performance than a raw score of 55 in an easier one. Standardized scores reflect this.

Once standardized scores are computed for each subject, the next step is to convert them into what are called T-scores. The formula for this is: T-score = 50 + (10 × Standardized Score)

This formula ensures that the scores are easier to work with and interpret. Instead of dealing with decimal values or negative numbers, the T-score transforms the standardized score into a scale centered around 50.

A T-score of 50 means a student performed exactly at the average level. A T-score of 60 means they were one standard deviation above the average; a score of 40 means one standard deviation below. This scaling helps education authorities to combine the subject scores more easily and apply consistent rules for placement in secondary schools.

Once T-scores for each subject are computed, they are combined—usually with different weightings (for instance, sometimes more weight is often given to Mathematics and English)—to arrive at the final composite score.

This scoring system, while complex, is rooted in fairness. It adjusts for variations in difficulty across the four subjects in any given year, ensures that high performance is recognized even when certain subjects prove more challenging, and prevents any single subject from disproportionately influencing a student’s overall result. More importantly, it means that scores between different years are not directly comparable.

So, when someone claims that this year’s top student didn’t do as well as last year’s because her overall score was “lower,” they are missing the point. The student reached the highest attainable T-score based on the standardized scale for this year. Comparing that to a raw or final composite score from a previous year—without considering test difficulty, student performance trends, and standard deviations—is both unfair and uninformed.

To draw a parallel: saying Usain Bolt ran slower in one race than another, without noting wind resistance or track conditions, doesn’t mean he was less exceptional. It means the context changed.

In the same way, the top NGSA performer in 2025 achieved a perfect score under this year’s conditions. There is no higher to go. And for that, she—and all top performers—deserve nothing but admiration.

So, let’s stop the misguided comparisons and start appreciating the brilliance of our young scholars. And while we’re at it, let’s thank Sir Leon for taking the time to explain a complex system in simple terms.

(The views expressed in this article are those of the author and do not necessarily reflect the opinions of this newspaper.)   

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• Comparing, National Grade Six Assessment, Peeping Tom, Perfect score

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