I think Auggie is feeling very upset and disappointed when jack will gave Auggie sort of like a death stare, Auggie felt a laugh cry emotion. That laugh cry emotion might feel like he is very sad and upset I have felt that laugh cry emotion before. It sort of feels like you are this big angry volcano then you see something

That reminds you about a funny moment that you can’t hold in.

That feeling he feels might make him very upset of his new school. Julian was being a big fat jerk when he asked Auggie about his face. At that moment Auggie felt very lonely and he might have also felt that laugh/Cry emotion again.