Our school system has limited resources for gifted kids in K-3 so cluster grouping has been our only support. There are four kids in my child's grade that perform at a level much higher than the rest of the students. The parents all "indpendently" met with the principal to request that the students be kept together for academic instruction. The other are exactly right in that the teacher must know how to differentiate and be willing to do so for this (or anything else) to be effective. We had great experiences in 2 grades. One year we hit a brick wall because the teacher did not understand how to curriculum compact. Best of luck with your efforts to make it happen!