What happens in chapter 11 of Firegirl?

In chapter 11 of Firegirl, Jessica sits at her desk and opens her pencil case; a photo flutters to the floor. Tom immediately picks it up and begins to ask Jessica about it. Other students also crowd in and speculate as to the identity of the people in the photograph. Before they know it, the students are actually talking to Jessica; one asks Jessica if the girl in the photo is her sister, and Jessica confirms that she is. Tom steps back for a moment and notices that this is the first time that anyone in class has spoken to Jessica in a relatively normal way. It is a reminder of how things used to be and how much he wants things to be the same again:

It was what everybody felt when Jessica wasn’t in school for a day. Only this was a hundred times better. We didn’t have to pretend she didn’t exist. We suddenly found a regular thing about her—her sister. Her sister wasn’t burned. Anne was a normal girl.

Now that the air has been cleared, everyone is mostly chatting about normal things, such as summer vacations—that is, until some classmates keep asking Jessica probing questions about Anne, and Jessica must confess that her sister Anne has died. Jessica looks visibly upset and asks Mrs. Tracy if she can be excused from class. Mrs. Tracy gives Jessica permission, and Jessica leaves.