If you're not advocating for a skip but just subject acceleration, I think 80% is perfectly reasonable. There will be plenty of kids in that class that didn't score 80% on the end of the year test and were moved up anyway because that is the age-appropriate placement, particularly in elementary school.
I always tell people we know to push for 80% and accept 85% but to refuse 90%, especially if the test is multiple choice and less than 30 questions. I want wiggle room for gifted kids who may miss 1 problem for not reading the directions all the way, 1 problem for moving too fast and transposing numbers and 1 problem for overestimating the problem and not solving it with the "too easy" answer.
