Jack admits that he's a hypocrite and didn't sit with August on the first day of school because he just wanted to be normal for a little while. He was surprised when Summer sat with August and figured that she was just doing it to be nice. Now, Jack tells them what Charlotte shared about Julian's vendetta, though he leaves out stuff about the holiday party, Julian's mom saying that August has special needs, and the rumor that he snapped because of pressure to be August's friend. Jack muses that it's weird to have people ignore him, and August sarcastically says, "welcome to my world."
Remember that Via conceptualized August's sarcasm as new and different; this suggests that August is beginning to come into himself and take on this sarcastic persona as a part of his new, more mature identity. When Jack leaves out information that would hurt August's feelings even more, it shows that he too is coming of age and learning more about how to be kind and take care of his friends.