Nancy Carlson 
Loudmouth George and the Sixth-Grade Bully, 2nd Edition 

The first day of school can be scary enough as it is without a bully stealing your lunch! And that’s just what happens to poor George when he runs into Big Mike, the sixth-grade bully, on the walk to school. Every day George is tormented-not to mention hungry-and too afraid to tell anyone, until his good friend Harriet steps in and helps George give Big Mike a taste of his own medicine.