ETA: I may push that she goes to a higher grade for reading because she's already the highest reader in her class and the students in her reading group aren't near as advanced as she is...
I think your daughter deserves to read with other children who are at a similar level of readiness. I wouldn't push directly for them to test her reading above level - I would push for them to teacher her at her current level with peers - so yup, then get to have the 'bright idea' to test her above level and use their own tools to shed light on this concern.
You can start the conversation by pointing out that the books she chooses and enjoys from the library are: and list 5 recent favorites. You can probably also google the names of the books and 'lexile' or whatever system they are used to.
I use the analogy of 'shoe size' I don't care what the number is that is stamped inside the shoe, I want a shoe that fits and supports my feet.
Good luck!
Grinity
