Understanding Grades, Part One

Grading completely confuses students, parents, and even some teachers. I will try to condense 20 years of hard-won knowledge into a few, pithy blog posts.

Today, I will focus on “grade weights.” I’m not talking about having honors level courses be worth more points in the GPA than general courses. That’s a different story for a different day. What I AM talking about is when a teacher weights his/her various types of grades within a course.

Years ago, (okay, about 5), before parents and students had such intimate access to a teacher’s grade book, lucky parents saw graded papers come home, and thus had a way to estimate their children’s academic progress. By the time the student reached high school, parents pretty much received an interim and final grade for each course. Parents had to trust teachers’ professional training and experience to accurately assess students’ progress.

Fast forward to today. Parents and students can see every single point on every single assignment, but they frequently do not know how to interpret their results.

So here is the basic explanation:

Grade books are set up in one of two basic ways: points or percentage.

1.) Points: Points are simple. Each assignment in a course is worth a certain number of points. The teacher divides the total number of points earned by the total number of points possible, and the result of that simple calculation is the grade.

For example: I have 500 total points possible in a quarter. A student earns 475 of those points. 475/500=95. A grade of 95 is equivalent to an “A.”

A trickier way to use points is to convert each grade into a GPA type grade, such as  a “B”=3.0 and an “A”=4.0. Averaging the two gives a 3.5 GPA for the course, which is the equivalent of a “B+.” This process is a complete pain in the neck, and it is also hard for parents and students to understand. I prefer to K.I.S.S. (Keep It Simple, Stupid) to facilitate communication.

2.) Percentage: Percentages are very easy for parents to understand. All grades are converted into percentages, and then the percentages are averaged to calculate the final grade. Percentages work well in classes where all of the tasks are similar in difficulty and importance.


For example: A student earns three grades: 85%, 95%, and 100%. The average of these three grades is 93%, which is an “A-.”  


Percentages have one horrid pitfall. Recovering from one missing or poor assignment is almost impossible. For example: If the same student has one off day, and does uncharacteristically poorly on one assignment, his/her grade could be ruined. For example: The student earns three grades: 100%, 100% and 10%. The average for the class is 38%, which is an “F.”  When using percentages, teachers must be vigilant to ensure that one poor, “outlier” grade does not tank the entire quarter.  Two ways to handle this situation are to drop the lowest grade per quarter and to “cap” the bottom failing grade at 50%. In the example above, 100%, 100% and 50% averages to an 83%, which is most likely a more accurate assessment of the student’s mastery of the coursework.


Here’s where it gets confusing.


Now, we add in “weights.” In each class, a teacher can decide to make categories to separate different types of academic tasks. The teacher averages each category separately, and then the average for each category is assigned a “weight,” which indicates what percentage of the final grade that category is worth.


For example:


Quizzes= 20%

Class work=20%



So, if a student averages:

Tests: 80%

Quizzes: 90%

Class work: 100%

Homework: 25%



Tests: 80 x 5 parts= 400

Quizzes: 90 x 2 parts= 180

Class work: 100 x 2 parts= 200

Homework: 25 x 1=25


Total: 805/10 parts= 80.5 for the class grade.


The only caveat with this method is that teachers must ensure that each category has a sufficient number of grades to accurately assess the student. For example, if a teacher only gives one homework assignment, and the student forgets to do it, the best grade the student can hope for is a 90, even if he/she earns 100% on every other assignment in the entire quarter, and the teacher has had 10 tests and 20 quizzes. Thus, a single missing assignment can completely hijack a grade.

For further clarification, this website, Education Oasis, has a very simple reference guide.

Tomorrow, I will tackle the age-old question, “What do grades really mean?”