Initially, Pete is morose because he can't gain the attention of Maybelle, the beautiful girl in his science class; she is two years older than he is, and all the boys admire her. Maybelle seemingly doesn't even realize he's alive, and Pete has no choice but to admire her from a distance.
Suddenly, things begin to shift. Maybelle begins showing Pete some attention, likely because she wants to copy his homework each morning; Pete is more than happy to comply with her wishes but doesn't seem to perceive that she could be using him. For four or six weeks, she hangs out with Pete outside of class and even allows him to take her on a few dates. She clearly isn't incredibly infatuated with Pete; he points out that during their private time, Maybelle "acted as though she really cared for [him] a little."
It isn't long before Maybelle's attention shifts away from Pete altogether and she begins riding around with a football player who drives a yellow roadster. She still hangs out with Pete from time to time, but she spends that time being "snippy" or ignoring him completely. Meanwhile, Pete notices the way she gazes longingly into the eyes of the football player while the two of them ride around. After keeping Pete on the sidelines while she enjoys the company of another boy, Maybelle finally tells Pete that she never cared about him and that she is sick of Pete being around her all the time.
Pete is humiliated, because he had believed that Maybelle enjoyed his company, even in the smallest ways, and that there was a chance that they could have a meaningful relationship together. Yet by openly dating another boy and ignoring Pete even when she was on dates with him, Maybelle made it clear that Pete was simply not important to her. She used Pete for a time, and when his value faded, she simply moved on to someone with a flashier presence.