Ch.22.3. How does Atticus justify to Aunt Alexandra Jem and Scout's attending the trial?

Alexandra disapproved of the children attending the trial and believed they should be sheltered from it. Atticus says the children need to be aware of the world they live in as much as they need to be expsed to the reality of their town as much as they need to be exposed to the world discussed at missionary teas.

“He’ll be so presently,” said Atticus. “It was a little too strong for him.” Our father sighed. “I’m going to bed,” he said. “If I don’t wake up in the morning, don’t call me.”
“I didn’t think it wise in the first place to let them—”
“This is their home, sister,” said Atticus. “We’ve made it this way for them, they might as well learn to cope with it.”
“But they don’t have to go to the courthouse and wallow in it—”
“It’s just as much Maycomb County as missionary teas.”