One of the major themes of chapter ten is that of the children's dissatisfaction with their father. They feel like he is a little bit old and feeble and that the town doesn't know how great he is. They talk to Miss Maudie about it and she points out all the great things that Atticus can do but these are not impressive to the children. It is lost on them but Atticus has shown one of his moral virtues is that he is not out for praise or recognition but that he quietly does a good job and does not boast.
Later in the chapter when there is a rabid dog loose on the streets, Atticus shows his calm under pressure when he is asked to take the shot. The children see this and are impressed but it also demonstrates that Atticus is calm under pressure and that he has skills that people know but that he's never shared with them. This portrayal of him helps to demonstrate his modesty.