I agree with epoh. I don't think it's possible to start off ahead and not have extra gas in the tank, so to speak. These kids are wired differently.

My DD9 for example had/has MASSIVE anxiety issues so they strongly pushed to put her in a 2/3 split when she was in third grade. I knew this would be disastrous for her grades but I was desperate to address the anxiety so I trusted her grade 2 teacher who was advocating for this. Sure enough, her grade 3 report card was full of comments about how she had trouble focusing, was often lost in thought, and needed constant reminders to finish her work. Socially though she came out of her shell a bit.

In grade 4 I wanted to do it my way - I requested (and they complied) a 4/5 split. The class was mostly 5's and some kids were 2 years older. Sure enough, DD's marks improved and she was accepted into the gifted math program starting this month.

Anyway, frannie, just like your DD, mine had an academically disappointing grade 3, but it was because of her environment. Maybe the same is true in your DD's case?