Why are the shortcut to school and The Quarters important in To Kill a Mockingbird?
Harper Lee used locations likely to demonstrate social distinctions. Here are some valuable interpretations to those specific locations.
Understanding that the short cut to school led the children right by the Radley house meant that Boo might have watched the kids walk by there regularly. He knew their patterns to and from the school and this is particularly important when you look at what happened in chapter 28. He knew the kids were out there.
The quarters were behind the dump. One had to pass the Ewell's home to get to the quarters which meant every Negro who lived in the Quarters passed the Ewells going to and from work. This is of particular concern because Tom's accusation arises from where his daily journey took him, and later in the story, where his wife's daily journey took her. Had Tom not passed the Ewells daily, they wouldn't have been able to craft and create this trial.
The shortcut to the school in Harper Lee's novel, To Kill a Mockingbird, is also important because it gives Bob Ewell a slightly less public opportunity to attack Jem and Scout. The darkness and lack of street lights makes it a practicable place for him to successfully murder the children and make good his threat to Atticus. Luckily for the children, Bob did not count on Boo Radley keeping a wary eye out for their safety.
The Quarters is also important because it marks a distinct separation between the African-American community and the white area of Maycomb. This division of the two races is an important theme of TKAM and the area serves as a kind of dividing line between black and white. The Ewells, the trashiest of Maycomb's white families, appropriately live near this divide--adjacent to the town dump.