#3 The Secret at the Polk Street School by Patricia Reilly Giff, 1987.
Dawn’s class is competing against other classes in a contest to see which class does the most for the school. All of the classes are working on their own special projects, trying hard to keep them a secret until the judging. Dawn, as the class’s resident detective, suggests that she could solve a mystery on behalf of the class, but unfortunately, there is no mystery for her to solve. Yet.
Instead, Ms. Rooney’s class decides to put on a play for the rest of the school. It’s Little Red Riding Hood, and Dawn is playing the starring role. Jason gets to be the Wolf, borrowing an old wolf costume from his sister without her permission.
At the class’s rehearsal, Dawn gets mad when someone dressed in the wolf costume tries to scare her, and she thinks that it’s Jason, goofing off. But, it turns out that Jason wasn’t even there, and the wolf costume is missing. Suddenly, Dawn has a mystery!
Dawn starts receiving messages from “The Wolf” saying that someone is going to get her and Jason. Then, someone takes a bite out of the loaf of bread that Dawn has been using as a prop (the food that she’s taking to “Grandma’s House” in the play). Could “The Wolf” be someone in a rival class, hoping to sabotage their play so they can win the contest?