# Calculating Grades

For most GSIs, it is the Instructor of Record who establishes the grading scheme for a course. However, as you take on more responsibility for course design later on, you may want to know more about the choices you have and the assumptions those choices rest on.

The following material is based on *Effective Grading: A Tool for Learning and Assessment* by Barbara E. Walvoord and Virginia Johnson Anderson (San Francisco: Jossey-Bass, 1998), 93–104.

Walvoord and Anderson describe three basic models used to weight assignments and calculate final grades: weighted letter grades, accumulated points, and a definitional system.

## Letter Grades

In this model, each graded activity or performance or product counts for a fixed percentage of the final course grade. The instructor has decided that each activity is sufficiently distinct from the others to merit a differential value in the overall system. For example:

Paper/exam 1 | 20% |

Paper/exam 2 | 25% |

Paper/exam 3 | 35% |

Homework and participation | 20% |

Using this model, an instructor can give the early assignment a lower-stakes grade to allow for lower student skill levels at the beginning of the course, and reward improvement later in the course.

## Accumulated Points

Using this model, an instructor assigns a maximum number of points to each activity, performance, or product. However, the scale (the relationship of point values to letter grades) can be flexible.

The scale could be inflexible, for example 100 to 91 points = A, 90 to 81 points = B, 80 to 70 points = C, etc. In this case the point system becomes a variant of weighted letter grades (see above).

Flexibility comes in when, for example, an instructor decides that it is the overall performance in the course, not necessarily in each distinct component of the course, that matters most. If a student does very poorly in one course unit, she can make up for the low number of points scored in that unit by doing very well in another one. The points become, in a sense, transferable. One way to arrange this is for the instructor to make it possible to earn 1050 points in all the activities of the course, and stipulate that an A grade falls within the range of 901 to 1000 points. Fifty points are available to make up for a student’s low point in the semester.

Comparing the flexible accumulated points model with fixed percentages shows a distinct difference in instructional assumptions.

## Definitional System

In the definitional system the instructor defines a standard for each category of work for a course, and students have to meet those standards for every category. So, for example, let’s say that the instructor stipulates the following scale for the homework category:

Turn in 90+% of homework | A |

Turn in 80 to 89% | B |

Turn in 70 to 79% | C |

Turn in 60 to 69% | D |

The instructor also explains to students that without an A in the homework category it will be impossible to get an A in the course (since an A by the instructor’s definition means exemplary work in every aspect of the course). If a student gets As on all the other assignments but a B on the homework, then the final course grade is a B. This instructor highly values students coming fully prepared to each class meeting and makes it a priority through this definitional grading system. Homework (which usually translates to quality of class participation) has a decisive value in the final grade regardless of how a student performs on major assignments.

## Help Students Understand Your Grading System

Whatever model you adopt, you will need to make sure students understand how course grades are calculated and explain to them why you have chosen the model you have, weighted grades the way you have, and so on. Finally, develop a clear policy about extra-credit assignments and grade penalties, and distribute this policy to students in written form early in the semester. This heads off grade disputes later on.