At the end of the day, Jack finds a note from Charlotte in his locker asking him to come alone to room 301 after school. There, she swears Jack to secrecy and explains that at Julian's holiday party, everyone but Jack and August were there. Julian told everyone that Jack has emotional problems, that Jack's parents begged the school to not expel him, and that this all happened because Mr. Tushman forced Jack to be friends with August. Charlotte says too that Julian's mom is pushing the school to review August's application, since some assignments have changed a bit to accommodate him.
Though Charlotte is doing a noble thing by clueing Jack into what's going on, she clearly cares more about her own social standing than being kind given that she shares this information secretly and doesn't want her name attached to it. This again shows that even those who don't really want to participate in the social structure are often forced to participate anyway, if only because they fear being ostracized.
Charlotte says that it's dumb, but Julian's trying to "help" Jack by cutting him off and making him feel lonely. He thinks that it'll make Jack drop August if all the boys refuse to talk to Jack. She explains that the girls except for Savanna's group are neutral. Jack lies and says he doesn't care if nobody talks to him. They agree that Julian's mom editing the class photo was gross. When Charlotte leaves the room, Jack can tell that she doesn't want to been seen talking to him.