What promise does Scout make in Chapter 2 of To Kill a Mockingbird?

I'm not so sure Scout made any promises in Chapter 2 of
To Kill a Mockingbird. Jem made it clear to her that she was not to
have anything to do with him while they were at school: "I was to stick with the first
grade and he would stick with the fifth."

However, in
Chapter 3, Atticus gets Scout to promise him that if she continues to go to school, they
would continue to read together each night. It must be a secret kept from Miss Caroline,
though, since Atticus "wouldn't want her after
me."