Lin Yan came today specifically to proctor the exam.
Generally, students from the countryside that manage to get into Shengjing are placed in her Class E, with very few advancing to Class D.
That's why she personally came today—to strictly control the admissions into Class E.
Class E is essentially formed by students with the poorest grades at the beginning of the term, and their average score has always been the lowest in the grade.
This Lu Sheng isn't even an exceptional student; he was just average in a shabby rural school. If such a person were to join her class, wouldn't that just drag down the class average?
Lin Yan did not want, or should say, did not think highly of Lu Sheng, and did not want Lu Sheng in her class.
Since he is a liberal arts student, subjective questions in test papers have no standard answers, meaning there's a lot of room for scoring manipulation.