How does the girl in Ponyboy's class react when he uses a switchblade to dissect a worm?

The answer to this question can be found in chapter 1. Ponyboy is introducing readers to himself, his brothers, and some of the other Greasers. Additionally, Ponyboy is giving us a bit of background on the conflict that exists between the Greasers and the Socs and some of the basic differences that he sees between the two gangs.
At one point in the chapter, Ponyboy tells readers that he is working on some English homework. He's working his way through Great Expectations, and Ponyboy finds himself relating with Pip. Pip is immediately judged because he isn't a gentleman, and a girl is always looking down on him. Ponyboy feels this way, and he gives an example from his science class. He was dissecting a worm, and the blade he was given in class wouldn't cut. Ponyboy doesn't even think twice about pulling out his switchblade to do the task, but the girl next to him is shocked and a bit scared. To her, the blade simply confirms her preconceived notions about who and what Ponyboy is.

The minute I flicked it out—I forgot what I was doing or I would never have done it—this girl right beside me kind of gasped, and said, "They are right. You are a hood."