It looks like the performance page is counting the scores for cohort students not in the class as 0. I tried comparing the performance of a class, two students in the class, and a cohort containing those two students plus others not in the class. The graph for the cohort was much lower than the average (around 10% vs. 55%).
It looks like the performance page is counting the scores for cohort students not in the class as 0. I tried comparing the performance of a class, two students in the class, and a cohort containing those two students plus others not in the class. The graph for the cohort was much lower than the average (around 10% vs. 55%).