Roll of Thunder, Hear My Cry

i have a few questions what did the night riders do to Sam Tatum. Why dose mama whip Stacey in front of the class. Why dose Cassie get mad at me burnet In the store. Who dose Cassie bumb into on the side walk and lastly what dose Stacey mean when he said about t.j. , “what he got comming to him is worse than a beating? If anyone can answer these questions it would be greatly appreciated