When scout introduces walter to her teacher by saying, "miss caroline, he's a cunningham," what does scout assume that miss caroline will automatically understand about him? what characteristics do the residents of maycomb automatically associate with "the cunningham tribe"?

By being known as "a Cunningham" and easily recognized by their last name, the citizens of Maycomb know this family fairly well. They lived on farms in the northern part of the county. In the novel, the Cunninghams were known as a rough crowd to hang around with. They gambled, drank whiskey, and would often hang out in a few of the same places (and everyone tried to avoid those places).  They were part of the wrong crowd and just bad company to be associated with. 

However, the reputation of the Cunningham clan did have some positives. They weren't known to be aggressive or abusive. They were known for never taking favors that they couldn't pay back. While not used to mainstream social life and immersed in their country/farm life, Cunninghams were simple folk who were honest and understood the value of hard work. These characteristics are known to the residents of Maycomb, including Miss Caroline. When Scout introduces Walter to her, Miss Caroline can make some of these assumptions based on the history of the Cunningham family that Walter comes from.