Unfortunately, being told that a child must be consistently scoring at 100% before a school would consider acceleration is not uncommon. This stance by a school can fuel perfectionism, while "treading water" and not learning challenging new material can fuel underachievement.
Knowing that each year most children are routinely promoted to the next grade with less than 100% mastery (as 76%-79% is often considering a "passing" grade) some families have successfully advocated for their gifted or high-achieving children to take the school's end-of-year tests early to grade skip (one grade level or more).
Others have had success with out-of-level academic talent search tests and the accompanying results reports with suggested academic placement.
The Iowa Acceleration Scale is another option which some schools have utilized to develop confidence that grade skipping is a viable educational path to offer a particular student.
Not saying that this is necessarily applicable to your dd, or applicable at this time, with this school, etc. Just sharing an alternative view that families need not be dissuaded from considering acceleration if a school's initial response is negative or consists of setting the bar unusually high.
