why does little man throw his school book onto the floor and stomp on it

Little Man reluctantly takes a book from those available, but after he flips through it, he sees a chart inside and throws it on the floor angrily. The chart denotes the book's condition, and the race of the student who is using it. When Cassie looks at her own book, she realizes what made him so angry; the last entry reads, "nigra." Both Cassie and Little Man refuse their books.