Welcome!
You've received great advice above.
If the scores indicate your child is in the
99.9th percentile according to the information provided on this webpage, you may wish to apply to the Davidson Young Scholars (DYS) program.
To prepare for your GIEP meeting, you might want to read this post of
buzzwords and their meanings, especially looking at pull-out groups and differentiation as you mentioned that this what you anticipate may be offered by the school.
In general, many parents find that their gifted children are not well-served by the government school system, which is focused on closing achievement gaps and excellence gaps (therefore may cap the growth of students at the top to accomplish this gap closure: equal outcomes is their goal).
What is the downside of a child not being challenged in school? Students may grow unmotivated by lack of an academic challenge worthy of their potential; They may stop learning and "level out"... They may find ways to entertain themselves in class and be labeled as class clowns or disruptive...
- This
old post summarizes ten key points made in the linked article: What A Child Doesn't Learn.
- This
old post discusses excerpts from a linked article on the downside of having a poor educational/academic "fit".
Armed with the knowledge from these links, during your meeting you'll want to take notes, and ask gently probing questions.
Here is a link to a post which contains a roundup of
advocacy tips.