Answer:
The sentence in question shows the dynamics of the relationship between teachers and students: the student, in general, devalues the teacher's knowledge, partly due to the immaturity of his age and partly because the contents of the classes tend to be unattractive for them, who have interests commensurate with their age. However, this disinterest of the student disappears at the moment in which the teacher evaluates the knowledge, as they realize the interest that the teacher has regarding the knowledge and learning of the contents.