Lilly has a fierce admiration for her very cool teacher, Mr. Slinger. Then one fateful day, Lilly shows up with a totally fashionable purple plastic purse (accompanied by "glittery movie star sunglasses with real diamonds"). She, of course, is feeling that she's the height of mouse fashion and glamour, but Mr. Slinger puts a stop to that. He irritates her by taking away the glasses and purse when it's clear that they're impeding Lilly's attention in class. Lilly is furious and takes out her anger on Mr. Slinger in a sneaky way. He meets her anger with patience and understanding, and she is apologetic. All's right with the world by the end of the book.
Henkes has a marvelous and intuitive feel for the way little kids think and how they express themselves. That, combined with his completely charming drawings, means that "Lilly's Purple Plastic Purse" is a grand way to spend twenty minutes reading to the nearest mouse-loving kid.
As an educator, I think this book carries an important message to teachers. It reminds us that what we do matters deeply to children, even when they are angry at us, and that discipline can happen fairly and with kindness. Every teacher should strive to be a "Mr. Slinger."
