For example, let’s say the highest grade on a test was 95%. In this case, because 100-95 = 5, we would add 5 percentage points to all of the student grades. This makes the 95% score an adjusted 100%, and every other score 5 percentage points higher than it was. This method also works using absolute scores, rather than percentages. If the highest grade was a 28/30, for instance, you would add 2 points to the score of every assignment.

For instance, let’s say that the entire class missed one problem which was worth 10 points. In this case, you might choose to add 10 points to every student’s score. If you think the class doesn’t deserve full credit for the missed problem, you might also choose to only give out 5 points. This method is closely related to the previous method, but it isn’t exactly the same. Because this method doesn’t specifically set the highest score in the class as a 100% maximum score, it allows for the possibility that none of the assignments receive a perfect score. It even allows for scores over 100%!

For example, let’s say that a student completely bombs his first test, scoring a 0. However, since then, he’s studied hard, receiving 70% and 80% on his next two tests. Un-curved, he has a 50% grade right now - a failing score. If we set a lower limit on failing scores of 40%, his new average is 63. 3% - a D. It’s not a great score, but it’s probably fairer than failing a student who’s shown real promise. You may choose to set separate lower limits for assignments that are turned in vs. assignments that are not. For example, you may decide that, for failing assignments, the lowest possible grade is 40%, unless it’s not turned in at all, in which case 30% is the lowest possible score.

Begin by determining the class’s mean (average) score. Add up all the scores in the class, then divide by the number of students to find the mean. Let’s say that, after doing this, we find an average score of 66%. Set this as a mid-range grade. The precise grade you use is at your discretion - you may want to set the mean as a C, C+, or even B-, for instance. Let’s say that we want to set our 66% as a nice, round C. Next, decide how many points separate the letter grades in your new bell curve. Generally, bigger point intervals mean that your bell curve is more forgiving to low-scoring students. Let’s say that in our bell curve, we want to separate our grades by 12 points. This means that 66 + 12 = 78 becomes our new B, while 66 - 12 = 54 becomes our new D, etc. Assign grades according to the new bell curve system.

First, choose 2 raw scores (actual student scores) and determine what you want them to be after the curve. For instance, let’s say the actual mean score on an assignment is 70% and you want it to be 75%, while the actual lowest score is 40% and you want it to be 50%. Next, create 2 x/y points: (x1, y1) and (x2, y2). Each x value will be one of the raw scores you chose, while each y value will be the corresponding score that you want the raw score to be. In our case, our points are (70, 75) and (40, 50). If you want a top score of 100% to stay as 100%, e. g. to avoid curving anyone’s score above 100%, you may choose your second point as (100, 100), even if no one earned a perfect 100%. Plug your values into the following equation: f(x) = y1 + ((y2-y1)/(x2-x1)) (x-x1). Note the lone “x” without any subscripts - for this, plug in the score of each individual assignment. The final value you get for f(x) is the assignment’s new grade. To clarify - you have to do the equation once for each student’s score. You can evaluate everything but the lone “x” to simplify before substituting the “x” for each student. In our case, let’s say we’re curving an assignment that got an 80%. We would simplify the equation one time, as follows: f(x) = 75 + (((50 - 75)/(40-70))(x-70)) f(x) = 75 + (((-25)/(-30))(x-70)) f(x) = 75 + 0. 83 (x-70) Then substitute x for each student and evaluate: f(x) = 75 + 0. 83 (80-70) f(x) = 75 + 0. 83 (10) f(x) = 75 + 8. 3 f(x) = 83. 3 . The 80% “raw” score on this assignment is now curved to 83. 3%.

In our case, let’s say we’re curving an assignment that got an 80%. We would simplify the equation one time, as follows: f(x) = 75 + (((50 - 75)/(40-70))(x-70)) f(x) = 75 + (((-25)/(-30))(x-70)) f(x) = 75 + 0. 83 (x-70) Then substitute x for each student and evaluate: f(x) = 75 + 0. 83 (80-70) f(x) = 75 + 0. 83 (10) f(x) = 75 + 8. 3 f(x) = 83. 3 . The 80% “raw” score on this assignment is now curved to 83. 3%.

Let’s say that a student scored 60 points out of 100 on a test. We give the test back to the student, offering half-credit for any problems she re-does. She re-works the problems she missed, scoring 30 more points. We then give her 30/2 = 15 more points, making her final score 60 + 15 = 75 points. Don’t allow students to merely correct the work they’ve done. Instead, to ensure they fully understand how to do the problems from start to finish, have them completely rewrite the items they missed.

Note, however, that this method gives extra weight to the questions you do choose to include. It may also anger students who did well on the questions you chose to eliminate - you may want to offer them some form of extra credit. Or, turn the tough question into a bonus question. If you are concerned about grades above 100% or grade inflation in general, you can set a policy that grades on any assignment are capped at 100%, 102%, etc.

However, use caution with this method - the students who probably need the most help are also the least likely to be able to answer super-hard extra credit questions. You may find that your extra credit assignments are more effective if they allow students to incorporate classroom concepts into outside-the-box projects and assignments. For instance, if you’re teaching a class on poetry, you may want to offer an extra-credit assignment that requires students to analyze the rhyme scheme of their favorite pop song.