Eleanor Estes’s The Hundred Dresseswon a Newbery Honor in 1945 and has never been out of print since. At the heart of the story is Wanda Petronski, a Polish girl in a Connecticut school who is ridiculed by her classmates for wearing the same faded blue dress every day.
Wanda claims she has one hundred dresses at home, but everyone knows she doesn’t and bullies her mercilessly. The class feels terrible when Wanda is pulled out of the school, but by that time it’s too late for apologies. Maddie, one of Wanda’s classmates, ultimately decides that she is "never going to stand by and say nothing again." (Amazon.com)