What happen in the middle part of the book?

In the middle of Andrew Clements's novel No Talking, the fifth-graders have their last day before they begin the challenge that the boys have made with the girls not to talk.
At Laketon Elementary there is a nickname that the teachers have for Dave’s class. Because the students are so loquacious and loud, they call them the "Unshushables.” So, when some of the teachers learn that all the fifth-graders are going to be silent, they are excited in their anticipation of a long desired break, especially at lunchtime. As the "No Talking" day approaches, no one is certain how the plan is going to work, including the anxious Dave. He worries about going home and how he will keep from talking; of course, he does not want to be responsible for the girls' winning the contest: "All over town, the other fifth graders are figuring out how to get along without talking" (Ch.14). Even at their homes, the students have problems because parents interpret their silence as an act of disrespect, or they worry that something is wrong. But, by the next day, the fifth-graders figure out how to communicate in different ways and how to follow the rule of using only three words if they must talk.