I'd talk with the teacher on or, preferably, before the first day, and bring in samples of what your child is working on at home, and ask if she can have similar work during at least a portion of the class time. For example, if the class is going over basic reading instruction, which your child clearly doesn't need, could your child have an advanced reading assignment to work on during that time, or a pullout to another classroom? Likewise, could your child have a math folder with advanced assignments that she does at the same time the rest of the class is practicing addition and subtraction? You might even want to volunteer to send these materials in, if the teacher seems to be overwhelmed by the request to differentiate.
All of that said, the teacher might smile and nod and agree and you still might not have anything like what you hope for materialize. Be prepared for a struggle if it happens, but don't go in assuming there will be a fight. But I agree that it is essential that you feed the fire while it is still burning.
