What causes Jem to strike out against Mrs. Dubose?
Atticus is constantly worried about how the trial is going to affect the children. He tells his brother, Jack,
"What bothers me is that she and Jem will have to absorb some ugly things pretty soon. I am not worried about Jem keeping his head, but Scout'd just as soon jump on someone as look at him if her pride is at stake..." (pg 88 - Chapter 9)
However, the person who does react and does lose control is Jem. Jem and Scout would have to walk by Mrs. Dubose's house on their way to town. They both hated her.
"If she was on the front porch when we passed, we would be raked by her wrathful gaze, subjected to ruthless interrogations regarding our behavlor, and given a melancholy prediction on what we would amount to when we grew up, which was always nothing." (pg 98)
One day, as they walked by her house, she said to them,
"Your father's no better than the niggers and trash he works for!" (pg 102)
Although they ignored her and continued to walk into town, the comment festered in Jem's mind. When they returned and passed her home once again, Jem grabbed the baton he had just bought Scout and ran into Mrs. Dubose yard. He swung at her camellia bushes and cut off all the tops. Scout says,
"By that time I was shrieking. Jem yanked my hair, said he didn't care, he'd do it again if he got a chance, and if I didn't shut up, he'd pull every hair out of my head. I didn't shut up, and he kicked me. I lost my balance and fell on my face. Jem picked me up roughly but looked like he was sorry. There was nothing to say." (pg 103)
Jem was obviously very out of control. When Atticus asks why he did it, Jem tells him of the comment Mrs. Dubose made about Atticus defending niggers and trash. Atticus makes Jem go over and apologize to Mrs. Dubose. He has to clean up the mess he made and garden for her until her camellia's come back. Mrs. Dubose also asks him to read to her. Atticus tells Jem,
"There is no point in saying you're sorry if you aren't...Jem, she's old and ill. You can't hold her responsible for what she says and does."
Atticus tells Scout,
"....when summer comes you'll have to keep your head about far worse things...it's not fair for you and Jem, I know that, but sometimes we have to make the best of things, and the way we conduct ourselves when the chips are down --- well, all I can say is, when you and Jem are grown, maybe you'll look back on this with some compassion and some feeling that I didn't let you down. " (pg 104)
The pages are from my edition of the book. They should be in the same proximity to the pages given.