You are graded for the quality of your work in presentations and general class participation, but this grade is not announced until the end of the semester, when it is recorded in your final grade report.

The reason for this “silent grade” is to avoid unproductive behavior from students in relation to the presentations, such as second-guessing, comparing grades, competing to each other’s detriment, or performing to the teacher. 

Altogether the presentations are a cooperative exercise on the part of the class, so it’s better to keep grading out of sight; however, since some students would work less otherwise, the leverage of a grade is necessary.