What does Little Chuck Little mean when he tells the teacher that Mr. Ewell is “right contentious”?

When Little Chuck Little refers to Bob Ewell as "contentious," he implies that the man is combative and likely to provoke conflict.
On Scout's first day of school, a new teacher introduces herself as Miss Caroline Fisher. She is from hundreds of miles away, a northern county with a different history and cultural past from the rest of the state. Because she is unfamiliar with the people in Maycomb, Scout tries to explain some things about the students to her teacher. Older boys and Little Chuck Little also try to tell her about the Ewells.
After the lunch period, Miss Caroline walks past Burris Ewell, and an insect creeps out of his hair. Startled by this action, Miss Caroline screams, "It's alive!" Thinking she has seen a mouse, Little Chuck Little asks where it went. He calls to a classmate, "D.C. shut the door, and we'll catch him." While the boys think she has seen a mouse, Miss Caroline says, "I was just walking by when it crawled out of his hair . . . " Always the little gentleman, Chuck escorts Miss Caroline to the front of the room and gets her a cup of water.
Having recovered herself, Miss Caroline asks the infected boy his name. After he tells her it is Burris, but he does not know how to spell it, Miss Caroline says that he is excused to go home and wash his hair. Further, she asks him to bathe. Burris responds with great disrespect, saying he is finished for the year, anyway, and he gives a "short contemptuous snort."
Miss Caroline is perplexed, so one of the older boys explains that the attendance officer can only get them to come on the first day, and their teachers just mark them absent for the rest of the year. "But what about their parents?" Miss Caroline asks. It is then that Chuck explains that the Ewell children have no mother and their father is "right contentious," implying that the attendance officer does not wish to battle with him.