Sammy Keyes and the Dead Giveaway by Wendelin Van Draanen
No good deed ever goes unpunished, Sammy discovers as she walks an elderly friend's dog straight into another mystery. Someone is trying to force the older woman and her neighbor out of their homes so a new rec center can be built. Even though Sammy's all for upgraded sports facilities, she can't stand silent when the methods used are underhanded. It turns out to be a little harder to speak up, however, when she accidentally kills her teacher's pet bird and her arch-enemy sets herself up to take the blame! Will Sammy still do the right thing when it's her own neck on the line? Recommended for grades 6 and up.