Grade curves seem like they should always help students. After all, if everyone does poorly on an exam, doesn't a curve bump everyone up? The reality is far more complex. Grade curves can help some students while hurting others, depending on your performance relative to the class average.
How Grade Curves Actually Work
The most common curving method is adding points to everyone's score. If the class average is 72%, a professor might add 8 points to make the average 80%. If you scored 72%, you'd jump to 80%. If you scored 92%, you'd jump to 100%.
Another method involves recalculating the grade scale. Instead of A being 90-100%, a professor might adjust it to 85-100% if the class average was low. The bell curve method assumes grades should follow a normal distribution, adjusting scores so roughly 15% get A's, 35% get B's, 35% get C's, and 15% get D's or below.
When Curves Help Your Grade
You benefit most when your performance is close to or above the class average. If everyone scored poorly and you scored at the class average, a curve helps significantly. If the class average was 68% and a curve adds 12 points, your 68% becomes 80%.
Curves help more when class performance is universally poor. If the entire class struggles, professors often use curves to prevent widespread failure.
When Curves Hurt Your Grade
You suffer most when you perform significantly above the class average. If you scored 92% where the class average was 72%, and a curve adds 8 points, you only reach 100% while the class average jumps to 80%. Your advantage shrinks.
With bell curves, if the professor wants exactly 15% of the class to get A's and you're the 16th percentile, the curve might cap your score at 89%, preventing you from reaching 90%.
Common Curving Situations
The most common situation where curves help is after difficult exams. If a midterm is harder than expected and the class average drops to 65%, most professors curve to avoid widespread failures.
The most common situation where curves hurt high performers is in highly competitive classes. In pre-med biology, professors sometimes use bell curves to maintain a specific grade distribution. A 94% might get you an A in a non-curved class but an A- in a curved one.
How to Tell If Your Class Uses Curves
Check your syllabus for mentions of curving. Many professors explicitly state whether they curve. If your professor says "grades may be curved if class performance warrants it," they reserve the right.
Many professors don't mention curves, meaning they curve if needed but haven't pre-committed. The best way to know is to ask your professor directly.
Strategic Thinking About Curves
Don't rely on curves to save your grade. Study as if curves don't exist. If you're averaging 72% and hoping a curve bumps you to 80%, you're gambling.
However, if you know your professor uses generous curves and always adds points, you can factor that into your expectations.
The Bottom Line
Grade curves are nuanced tools that help some and hurt others. High performers should never count on curves. Average performers often benefit when class performance is poor. Low performers hope for curves but shouldn't plan on them.
The most important thing is to focus on your own performance. Study thoroughly, do well on assignments, and perform your best on exams. Then, if a curve is applied, it's a bonus.