Grading Guidelines


Correctness, design, and style are the three axes along which we assess student work. Correctness and style are autograded, but design is where you as a TF critique code and offer your qualitative assessment. Design is graded out of 5 points.

What is Design?

Design is about how a student has approached the problem: to what extent their solution is efficient, creative, and shows mastery of course concepts.

Guidelines on Awarding Points

Design points are not subtractive—that is, a baseline grade is not a 5 and earning a 3 does not mean that a student has “lost two points” on an assignment or “earned a 60%” (two common interpretations we hear from students). Rather, points are used to characterize the extent to which a student has met, exceeded, or fallen short of the course’s expectations.

5’s are rare, especially in the first weeks of CS50. They are reserved for work that greatly exceeds the expectations of the course. Though 5’s are not comparative (i.e., indicative of “the best in a section”), a good rule-of-thumb is that only a few 5’s, if any, should be awarded per section.

3’s and 4’s are awarded to work that demonstrates a good to great mastery of the given week’s concepts and problem set. A student’s benchmark for success is considered a 3.

1’s and 2’s are awarded to work that demonstrates a poor to fair understanding of the given week’s concepts and problem set. Awarding a 1 or a 2 indicates that there are substantial improvements to be made to the design of a student’s solution.

Grading FAQs

What if a student asks for an extension?

If a student asks for an extension, you should respond by directing the student to, highlighting in particular the clause that says “To grant yourself this extension, submit this form by the problem set’s deadline.” You should cc in your reply. All instances in which a student asks for an extension should include

How should I grade incomplete work?

If a student has submitted an incomplete solution, it is best to approach grading design in response to the question, “Given what the student has submitted, what evidence do I have that they have understood a good design approach to the problem?”. We want to avoid a scenario where a student is double-penalized for incompleteness, on both correctness and design, but we also don’t want to extrapolate from a single function that a student has understood all of the week’s design concepts.

How long should I spend grading?

This depends on the week! On average, aim to spend about 10 minutes per student in your section. Set a timer, if it’s helpful!

Grading Deadlines

Feedback on problem sets is due no later than 5 days (120 hours) after the original date of submission. This is the following Friday, 11:59pm, after a submission is due on a Sunday, 11:59pm. In any instance where you will be late on feedback, it is critical to let Carter know beforehand. We can work something out, but only if we know ahead of time.