Many GSIs like to give their students a statement of their grading philosophy, together with a sample set of criteria for each grade range. Even if you prefer not to do so, you should take the time to think about how you grade and why, and about the criteria that you use in giving each of the grades. Having clear criteria not only saves you time when grading, but it also helps to make the grading process more consistent. In addition, it enables you to explain very clearly to students the kind of work you expect from them and helps students understand why you have given their assignment a certain grade and how their work might be improved. It also enables you to clearly diagnose students’ strengths and weaknesses, and thereby to focus on improving the appropriate areas more effectively.

It is also important to discuss your standards and criteria with any other GSIs teaching the same course to ensure that grading is consistent between sections. The Instructor of Record for your course may set the grading criteria for course and section as well. If so, be familiar with these criteria and be able to explain them to students.

Below are sample statements of grading criteria from two disciplines.
Philosphy
Physics

From Philosophy

What Your Grade Means

A-range:

Papers: excellent exposition, clearly and concisely written, well argued, and displaying good original input from the student.

Exams: answers all parts of the question clearly and concisely. Shows good knowledge and good understanding of the material. Well argued. Where required, contains good original input from the student.

B-range:

Papers: good exposition, but lacks clarity and concision, or doesn’t have much original input, or offers poor support for important claims. (For instance, a truly excellent expository paper will earn you a B+; a fuzzy but accurate one will earn you a B-).

Exams: Shows a good knowledge and fairly good understanding of the material but either fails to answer some parts of the question or is unclear or is poorly argued.

C-range:

Papers: fails to understand some aspects of the material, or is very unclearly written.

Exams: doesn’t show a good knowledge of the material or fails to understand some important parts of it, or does not answer a significant portion of the question.

D-range:

Very problematical. [If you receive this grade, come and see me to discuss what went wrong and how we can avoid it happening again.]

F:

Papers: did not submit a paper; plagiarized material; made no effort to understand the material or shows no sign of having read it.

Exams: did not sit the exam; cheated in the exam; made no effort to understand the material or shows no sign of having read it; completely failed to answer the question.

From Physics — rubric for homework assignments

What your grade means (roughly)

A grade of 1 means the work demonstrates no understanding of the relevant concepts.

2 means the work demonstrates a poor understanding of the relevant concepts.

3 means the work demonstrates a fair understanding of the relevant concepts.

4 means the work demonstrates a good understanding of the relevant concepts.

5 means the work demonstrates a great understanding of the relevant concepts.