One source of confusion regarding education policy is a lack of clarity about what the purposes of public schools are. As I see it public schools (K-12) have two main purposes. First to attempt to teach all their students those basic skills needed to function well as an adult in the United States. Second to identify and sort out the brighter students. In practice current schools attempt both of these. However, particularly in the higher grades, they seem more devoted to the second. In fact they sometimes seem actively hostile to teaching anything practical. Hence for example the trend towards dropping driver's ed.
But many policy discussions seem to only consider the first purpose. Devoting additional resources to the slower students makes sense when they are learning important basic skills. It makes no sense for classes like plane geometry which have little practical value and are used almost exclusively for sorting out the brighter students. Pushing slow students into such classes is just foolish. They don't need additional confirmation that they aren't as bright as other students and even if through great effort and perseverance they actually learn the material it won't do them any good.