On their way to the Finch's house for lunch, "Jem made pleasant conversation" with Walter, "cordially" comparing stories about Boo Radley as they passed his house.
By the time we reached our front steps Walter had forgotten he was a Cunningham.
Once inside, Atticus and Walter "talked together like two men, to the wonderment of Jem and me." Jem's behavior toward Walter stems from his understanding of the Cunningham family. He knows they are poor but honest, and he sees that the puny Walter is underfed and no match for Scout, who is big for her age. Jem is old enough to realize that inviting Walter home for lunch is a fair way of repaying him for Scout's unhospitable manners, and though the two boys will never be close friends, Jem walks with Walter back to school while Calpurnia finishes her scolding of Scout.