In Chapter 9, there was a talk about ‘ negroes’ what have they been doing?

I think you mean chapter 8:

We'd seen the pictures of a bunch of really mad white people with twisted-up faces screaming and giving dirty finger signs to some little Negro kids who were trying to go to school. I'd seen the pictures but I didn't really know how these white people could hate some kids so much.

I don't have an answer but want to hear what other people think