Take a story's temperature by studying its tone. Is it hopeful? Cynical? Snarky? Playful?
Clinical, Distant
The tone of Cather's narrator is dry and factual, almost as though this is a set of notes written by a psychiatrist or detective at the conclusion of a case. You can check out "Narrator Point-of-View" for more about that, but for now, let's take a look at a passage from right near the beginning of the story:
When questioned by the principal as to why he was there, Paul stated, politely enough, that he wanted to come back to school. This was a lie, but Paul was quite accustomed to lying—found it, indeed, indispensible for overcoming friction. His teachers were asked to state their respective charges, which they did with such a rancour and aggrievedness as evinced that this was not a usual case. (1.3)
Check out the weird way the narrator says "When questioned by the principal as to why he was there." Something just sounds a little odd about that, doesn't it? Notice that Cather doesn't say, "The principal asked him why he was there." Nope, it's got the passive grammatical structure that you find in a lab report or case study—and not usually in fiction writing.
Other phrases jump out here, too. "Politely enough" sounds like something one of his teachers said, like maybe the narrator was interviewing people to find out more about what happened. And then comes some more passive voice: "His teachers were asked to state their respective charges." And we wind up with the incredibly distant, clinical statement: "this was not a usual case."
What this passage suggests is that the narrator literally has no investment in the story, and no affection—or any emotions at all—about the characters. So, sure, she or he is probably a great doctor—but is s/he equally skilled as a narrator?