Atticus and their Aunt fought becuase their aunt wants Calphurnia to go away. She believes the kids shouldn't learn from her because she is black.  That is a bunch of crap.  Even though Cal is black, she is very "white" in the pressence of whites.  She knows what is proper and what isn't.  atticus decided she stays no mater what, because Cal means so much to their family.  Good for him, is what I think.