What does Becky Thatcher do that almost gets her into trouble?

well, in Tom Sawyer she found a book in the teachers drawer and was looking though it, Tom came up behind her and scared her causing her to rip the page she was holding out of the book. She knew she would get in trouble for it by the teacher and got really scared and that's when Tom came in and said that he did, taking Becky's beating for her.