Why do the other teachers consider Mama a "maverick"? How is her point of view different from Miss Crocker's?

Mama refuses to let her students be demeaned.  At school, Cassie and Little Man get in trouble with the teacher, Miss Crocker, by protesting that their used textbooks list the condition "very poor" next to their race. Mama, who is a seventh-grade teacher, pastes paper over the inside covers of her students' books to hide this information.