The issue of tracking-streaming-leveling, whatever you call it, is a knotty one. One thing we know for pretty much certain is that tracking hurts kids on the bottom. Once a child is placed in the bottom level, it’s almost impossible for them leave it, because opportunity to learn is decreased for the low-track students. I would argue it also hurts high track kids because they get an inflated view of their abilities, reinforcing their sense of privilege. Moreover, it is antidemocratic to provide opportunity to only some (who almost always are upper SES). On the other hand, a multi-leveled classroom requires an entirely different way of teaching, one that provides entry points for students of all prior achievement levels. The vast majority of teachers don’t know how to pull this off, and the result is harmful to high, medium and low students, as well as the teacher. My opinion, based on a lot of observation, is that traditional teacher-centered instruction well done is vastly superior to student-centered teaching of mediocre quality, a situation in which nobody seems to learn much of anything. In other words, I think reform pedagogies are more sensitive to the skill of the teacher. I seem in my posts to come back time and again for the need to transform teaching.
Education in the US, and in the countries which use European-derived systems of schooling, are based on the assumption that knowledge is an acquisition of information by individuals. We believe it is "natural" that some students learn better than others. Our entire education system is based on this belief. We develop standardized tests and have a multi-billion dollar industry based on this premise. However, in almost all learning situations outside of school, people learn new ideas and new skills through participating in the milieu in which they find themselves. For example, Mayan girls sit beside their mothers as they weave, help as they can, and over time begin to make their own weavings. No one "teaches" them. They learn through participating in village life. (This is documented by theorist Barbara Rogoff. Her book, The Cultural Nature of Human Development, is well worth reading.) Studies of non-school learning repeatedly show that teaching is not required for learning. Rogoff defines learning as "transformation of participation." In fact, all children who are not neurologically compromised accomplish the incredibly complex task of learning their mother tongue through their participation in family and community life, and do so without explicit teaching. How then, can we design educational institutions in which students are engaged in tasks where they can increase their competence? What sort of STEM tasks can children do that allow them to participate at more and more complex levels?
As far as transforming teaching, we need first to acknowledge the harm that the current view of learning causes. We also need to recognize that our assumptions about learning, when we investigate them, are simply not valid. Teachers need tools to understand the cognitive skills which each student brings to a classroom. They need to understand that ALL children are attempting to make sense of the schooling they receive. In this vein, I recommend Warren & Rosebery’s work. If you don’t know it, their edited book, Teaching Science to English Language Learners, is the result of many years of working with teachers to overcome deficit views of some students.