What was Calpurina's fault in the first few chapters of To Kill a Mockingbird?

You can find the answer to this in Chapter 2. What is
Calpurnia's fault is the fact that Scout can write.  Her teacher does not think she
should be able to read at this point and is upset that she
does.

Scout says that Calpurnia is the one who taught her
to write.  She says that Calpurnia taught her to write on rainy days.  She thinks that
Calpurnia did it to keep Scout from annoying her too much -- she just had her sit down
and work on her letters and copying passages from the Bible and other stuff like
that.