Thinking carefully, it does make sense. After all, Sophia, the Student Council President, was publicly stabbed to death by the Clown Grand Inquisitor a few months ago, making her an obvious dead person.
Although the death of a witch is common knowledge, they often rise again after a while, becoming a good girl once more.
However, a country cannot be without a ruler for a day, and a magical academy larger than most human kingdoms naturally cannot go long without a Student Council President either. So, in the absence of any signs of Sophia coming back to life for several months, the academy must have already elected a new Student Council President.
