Grades are based on applying the following schema to each student's participation in each class and then averaging across all classes (excluding the introductory 1st class).
5: Absent (up to a maximum of 4 times)
6: Present but silent
7: 2 or more ordinary contributions
8: 1 good contribution (that I consider particularly pertinent, thoughtful, and sophisticated)
8.5: 2 good contributions (or one 'excellent' contribution, which counts double throughout)
9: 3 good contributions
9.5: 4 good contributions
10: 5 good contributions
11: 7 or more good contributions
Obviously final grades cannot be above 10, but 10 is possible.