Why was Buris Ewel at school in To Kill A Mockingbird?

"He's one of the Ewell's, ma'am. Whole school's full of 'em. They come first day every year and then leave. The truant lady gets 'em here 'cause she threatens 'em with the sheriff, but she's give up tryin' to hold 'em. She reckons she's carried out the law just gettin' their names on the roll and runnin' 'em here the first day. You're supposed to mark 'em absent the rest of the year..." To Kill a Mockingbird, Harper Lee, page 30