Read the excerpt from "I'm Not Thirteen Yet" by Amy Bernstein. Sixth grade was a tough year. Some days, walking the halls was like trudging through peanut butter—nearly impossible. I had entered the world of teenagers, and I wasn't even one of them yet. Lynette Gardner had always been my best friend, until February, when she turned thirteen. I wouldn't be thirteen until August.

What central idea is being described in this excerpt?

the narrator’s struggle with a new school year
the narrator’s struggle with being a teenager
the narrator’s struggle with trying to fit in
the narrator’s struggle with succeeding in school