Going back to the scheduling of classes at the same time. You could do that for maybe 3 classes: math, LA, and either social studies or science. EVen within the same grade level, you could work out so that the most advanced in math go to the teacher that has a passion for math and/or is more qualified in math, then the same for the others. Kids rotate between these 3 teachers. For this to work, you might need to do a couple of grades at a time.
I know of a couple of gifted schools that deal with kids in the 130+ range, by sending kids to specialists starting around 4th grade; essentially the kids go from class to class, like middle schoolers. This allows for them to be taught by a specialist in the subject matter, which they require at that age. There is differentiation inside each section as needed. Teachers are trained to individualized curriculum to a certain degree(which would work for many in the 130-145 range). It might be hard for some of those teachers to provide materials/teaching to those who are too far ahead; some would find it doable and others would not.
