What happening caused Scout to feel "exhilarated" in Chapter 20?
In Chapter 21, Scout mentions that she is exhilarated when Calpurnia is taking the kids home from the courthouse. She is exhilarated because Atticus gave them permission to come back to hear the verdict. Atticus always encourages Scout to be curious and ask questions, which he answers as honestly as he would with an adult. However, Scout knows that Atticus wanted to spare the children any association with the controversy of the trial. It's not that he didn't want them to learn from it. Atticus just wanted to spare them any ridicule or physical harm (which eventually happened) as a result of being the children of the man who was defending Tom in a town with an unspoken racism. But once Atticus discovered that the kids had been in the courtroom already, he decided to let them come back for the verdict. Scout is thrilled because she is curious and likes to learn and the idea that Atticus initially didn't want the kids there just makes it more enticing for a child. Plus, she gets to see Atticus in action.