Are We in the Business of Sorting or Educating?

How do we group our students? In the article I Got Grouped, by Cris Tovani, she speaks of her foray into learning about technology. Often, especially in reading, we group students according to ability. How can we learn if we are surrounded by those all at the same level? She ends with this quote:

Being grouped refocused my attention on what matters most. I must make sure that my instructional practices match my beliefs about students' abilities. I must make available to students the tools, strategies, and experts that will enhance their learning. With scaffolded instruction, choice that drives engagement, and time to practice, our belief in our students' abilities can become their reality.-Cris Tovani