It's often been said that teachers actually learn more than their students. Perhaps, but at the very least, teachers learn as much as their students, and in very different ways. Teachers learn by being forced to have a more comprehensive understanding of the topic they are teaching. In addition, teachers get to work with a wide range of students, all with their own quirks and peculiarities. This experience works as a great index for helping the teacher to understand their own progress and struggles.
Every student becomes a possible comparison, a context for understanding the self.
The opportunity is too valuable to pass up. Although he has not yet passed the Subject A exam, he is actually quite bright. In fact, almost all of my students are very intelligent. Bob, in particular, has an encyclopedic vocabulary, and feels the need to demonstrate this in each paper. Bob also seems to have a secret fascination with writing three-page papers in a single sentence.