Sounds like they need an official policy. For example if a kid scores above X level on ability and achievement tests, they can be accelerated.
Our district has that but can't utlize it half the time, with conflicting schedules between classes. So if my DS was pulled out of class for math to go to a different grade, he would miss something else, like gym or music or lunch. So the school has a useless policy where some kids end up being able to take advantage of it and not others.