Explain the social consequences that Jem and Scout are facing because Atticus is representing Tom Robinson?
Because the town of Maycomb was segregated and still viewed blacks as second class citizens, the fact that their father was defending a black man against a charge of raping a white woman meant that anyone associated with Atticus could be viewed negatively. It is the idea of guilt by association. Add to that the fact that Atticus was raising his children as a single father, he let Scout dress in tomboy clothes, he allowed Calpurnia, a black woman, to "mother them" even going so far as to let her take them to her church, and several other "non traditional" behaviors condoned in the Finch family and what you have is a recipe for ostracism. Scout tended to fight back. She was not afraid to get in fistfights, as she did at school when the children teased her for being Atticus' daughter. Nor was she afraid to speak her mind when the lynch mob came after Tom and tried to get through Atticus. Scout had both a youthful innocence and a wisdom beyond her years. She realized that Tom was innocent, saw the injustice that was being perpetuated, and tried in the only way she knew to get the people (in this case the men of the lynch mob) to realize that what they were doing was wrong. Although she is unable to save Tom (not is Atticus able to), she still is able to salvage some shred of hopefulness due to the fact that it is Scout who realizes that Boo Radley was her savior, and because of what she has learned from her own time as outcast, she is able to see him for the "mockingbird" that he is. Jem's understanding of it all is a quieter understanding. This is due in part to the fact that he is older and wants to be like his father in terms of the way that he handles things, but much of his silence is a facade that he wears to deal with a reality that he views as morally wrong.
Dill's appearance in Maycomb offers Scout a neutral outsider's perspective on the town and what is going on in it. What makes this summer different from the last is that it marks an end of innocence. She has been sheltered from the harsh truths of reality up until this point. Now, she takes her first step on the road to adulthood as she begins to see what Maycomb is like, what expectations and stereotypes she will have to fight against as she grows into what we can imagine from the tone of the narrative is an independent woman. As an adult looking back, she sees this summer as a time of transition and of growing up, perhaps too soon, and a first step on the road to the woman she becomes.